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(CNN) -- "Our objectives are to strike London with low-cost operations that would cause a heavy blow amongst the hierarchy and Jewish communities, using attacks similar to the tactics used by our brothers in Mumbai."

Those are the opening words of a document found on the body of al Qaeda's top East Africa operative when he was killed two years ago.

And the plans uncovered in the document are now even more interesting and relevant in light of the attack on the shopping center in Nairobi, Kenya.

Among the targets identified: the famous Eton College, the five-star Dorchester and Ritz hotels, and the Jewish neighborhood of Golders Green in north London.

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The Word document, written in English, which CNN understands was stored on a thumb drive, was found when Fazul Abdullah Mohammed -- architect of the U.S. Embassy bombings in Nairobi and in Dar es Salaam, Tanzania, in 1998 -- was killed at a government checkpoint in the Somali capital, Mogadishu, one night in June 2011. Its contents were first reported by Michelle Shephard of the Toronto Star, who provided the document to CNN.

Read the document here on The Toronto Star

Richard Barrett, the fomer head of Britain's MI6 counterterrorism agency, told CNN that while the plans were "pretty aspirational" they were found on "a very determined and extremely able operator who could convert plans to reality" and were seen as a "significant warning" by Western intelligence agencies.

It's not clear whether Mohammed wrote or had approved of the plan. Its style and content suggest that it may have been a "pitch" to him by another al Qaeda operative. Shephard says that it may have been written by a British jihadist in East Africa.

But after the Nairobi attack by the Somali jihadist group Al-Shabaab and other al Qaeda documents seen by CNN, it is further evidence that replicating the 2008 Mumbai, India, attacks has become a major priority for the terror group, aiming at "soft" targets such as hotels, shopping malls, resorts or even cruise ships.

Barrett told CNN that the attack plans discovered in Mogadishu will now be seen in a more concerning light by Western intelligence agencies though "it is open to doubt" that Al-Shabaab would currently have the capability to carry out such an attack in the UK.

In a message to affiliates earlier this month, al Qaeda leader Ayman al-Zawahiri called for "taking the citizens of the countries that are participating in the invasion of Muslim countries as hostages so that our prisoners may be freed in exchange."

Attacking Eton College, where members of the royal family and British aristocracy are educated, would "strike a heavy blow at the 'who's who' of the political and business world," the document said.

"As we know the average English man is envious of the rich and has no ties to the upper class. This attack will totally infuriate the government/royalty but will not have such an impact on the masses," it reasoned.

As for the planned attack on either the Ritz or the Dorchester hotels -- which the author envisaged being carried out on "New Year's, Valentine's Day or even Hanukkah" -- there were further similarities to the attacks in Mumbai and Nairobi.

"We plan to book in advance and take plenty of petrol with the brother, then set the 1st 2nd and 3rd floor on fire using petrol and igniting using petrol bombs ... while we block the stairs so no-one can run down by blocking the staircase with furniture."

The author envisaged using Western recruits to carry out the attack, including British militants who had joined jihadist ranks in Somalia and people put forward by Al-Shabaab.

"For this mission we can use our own people or the harakah (Al-Shabaab) can supply suitable candidates or we would need instant access to all British muhajireen (jihadist emigrants)" the writer said.

"Each martyrdom seeker will be trained in Somalia preferably for 2 months ... the brothers will be pushed through many battles to see how they react under pressure and they will be analysed to see if they can keep their composure."

The training outlined in the document is a chilling precursor to the planning involved in the Nairobi attack.

The brothers "will be trained how to raid a house, clear rooms and gather all hostages in one room also how to use a human shield while shooting and moving through a building," it says.

"Reconnaissance will cover how to gather suitable information on the target, for example where are the nearest police stations, what times is the area most crowded, when are best times to attack, are there any armed guards, are they prepared for an attack, best way to enter building," it continues.

The Al-Shabaab attack in Nairobi closely mirrored the Mumbai attacks, in which members of the Pakistani group Lashkar-e-Tayyiba, a terrorist outfit affiliated with al Qaeda, seized hotels and a Jewish center and held out against Indian security forces for three days. More than 160 people were killed.

The similarities are striking:

• The targets were "soft" -- not military or government facilities, and therefore more easily penetrated;

• They were also enclosed, making it more difficult for security forces to flush out the assailants;

• A similar number of attackers -- about 10 -- was involved, and they used multiple entrance points;

• Both attacks were low-tech, involving automatic weapons and hand grenades, at the opposite end of the terror spectrum from the 9/11 attacks;

• Both involved a significant amount of preparation.

• They were in major cities, in places that attracted foreigners, and especially Westerners, and they focused on neighboring countries regarded as hostile. The Pakistani group attacked Indian targets; the Al-Shabaab cell attacked a Kenyan landmark in retaliation for Kenya's incursion into and occupation of southern Somalia;

• Israeli or Jewish interests were part of the targeting matrix;

• The attacks were geared to gaining maximum publicity.

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Resemblance to plans for European, U.S. strikes

Similar priorities appeared to have influenced another senior al Qaeda planner, Younis al Mauretani, who orchestrated a plan to hit Europe with a series of strikes, including Mumbai-style gun attacks. The discovery of the plans led to the United States issuing an unprecedented warning to its citizens in Europe in October 2010.

Western counterterrorism officials told CNN that al Qaeda at the time also envisaged hitting the United States with coordinated gun and hostage attacks. When U.S. Navy SEALs raided Osama bin Laden's compound in Abbottabad, Pakistan, they retrieved a letter Mauretani had written to bin Laden in March 2010 outlining attack plans. "After we hit Europe we will hit America," it said.

According to Swedish counterterrorism officials, in December 2010, a Swedish al Qaeda cell attempted to put part of the "Mumbai-style" plot into operation by driving to Denmark with a submachine gun, a silencer, several dozen 9 mm submachine gun cartridges, and plastic wrist straps to handcuff hostages. Their target was the Jyllands-Posten newspaper in Copenhagen, one of the newspapers that published controversial cartoons of the Prophet Mohammed. They were arrested once they reached the Danish capital. Security services believe the plan was to try to take up to 200 journalists hostage at the newspaper and execute many of them, a Swedish counterterrorism source told CNN.

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In May 2011, German police discovered a thumb drive hidden in the underpants of a terrorist suspect who was being questioned in Berlin. Encrypted deep inside a pornographic video called "Kick Ass" and a file marked "Sexy Tanja" was an internal al Qaeda document called "Future Works," which discussed seizing cruise ships and executing passengers, and carrying out attacks in Europe similar to the Mumbai attacks. Counterterrorism sources say another of the documents recovered contained notes in German, written at a training camp, on taking and executing hostages, putting the attack on camera and sending the video to al Qaeda so it could be used as propaganda.

U.S. intelligence sources told CNN last year that the documents, which included an internal report on terrorist plots that al Qaeda had orchestrated against the UK, were "pure gold."

While "Future Works" did not include dates, places or specific plans, it appears to have been a brainstorming exercise to seize the initiative and return al Qaeda to front-page news around the world.

Since then, drone strikes in the tribal areas of Pakistan have weakened al Qaeda's ability to execute complex attacks in the West. Letters recovered from Abbottabad suggested that al Qaeda leader Zawahiri thought the group could achieve more by prioritizing hitting Western targets in the Muslim world. In the last two years, he has also advocated lone-wolf attacks in the West by al Qaeda sympathizers.

The document found in the vehicle of Fazul Abdullah Mohammed, the U.S. Embassy bombings architect, also outlines plans for attacking Al-Shabaab's enemies in East Africa by storming the Ugandan, Burundian and Ethiopian embassies in London. "The brother would then enter the final buildings and hold hostages while killing them and fighting of[f] police," it says.

The document concludes: "As you can see we are planning to kill quality and quantity, not your average pig who is not valued by his own mother let alone the British government."

Mohammed's shaky Al-Shabaab connection

What's less clear is whether Mohammed was working with Al-Shabaab when he was killed or whether he had direct contact with al Qaeda central in the mountains of Pakistan. There is evidence that he had little time for Al-Shabaab or its leader, Mukhtar Abu Zubayr. He refused to join the group in 2008, writing: "As to taking orders from him or anyone else, this shall not happen because I am not part of the new group."

Mohammed preferred to lead an al Qaeda cell in East Africa. But counterterrorism officials believe that with his bomb-making expertise, he may have helped plan Al-Shabaab's suicide bomb attacks in the Ugandan capital in 2010.

His own voluminous writings, examined in detail by Nelly Lahoud at the Combating Terrorism Center at West Point, indicate that Mohammed saw Al-Shabaab as rash and ill-disciplined; he is likely to have supported bin Laden's decision to decline a merger between al Qaeda and the terrorist group. Some terrorism analysts say that Mohammed met his end just weeks after bin Laden was killed. Did Zubayr, who by all accounts was desperate to make Al-Shabaab an affiliate of al Qaeda, want him out of the way?

Who is Al-Shabaab's leader?

For a terrorist with his experience and ability, Mohammed's death seemed to have been caused by an uncharacteristic blunder. Some analysts believe Zubayr laid a trap by directing him to the wrong roadblock, or by removing an Al-Shabaab checkpoint so that Mohammed drove straight into the arms of government troops.

Whatever their relationship or rivalry, Zubayr soon got his way. In February 2012, Zawahiri formally announced that Al-Shabaab was part of al Qaeda. And Zubayr's attack on the Westgate Mall conforms exactly to Zawahiri's template for the future.

It is surely no accident that Zubayr, in his audio message claiming responsibility for the mall attack, invoked 9/11. For Western intelligence, one of the many alarming implications of the Nairobi attack is closer liaison -- operational and ideological -- between Zubayr and Zawahiri.

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