Early editions of The Observer, a national Sunday newspaper, said "terrorists linked to Osama bin Laden have drawn up plans for a devastating bomb attack on the City of London," the capital's financial district.
The 80-page document contained step-by-step instructions for constructing a remote-controlled van bomb like those used against the U.S embassies in Kenya and Tanzania in 1998, the report said.
A scribbled note on one page suggested the target was Moorgate in the center of London's financial district, The Observer said. Moorgate is a banking and insurance area and the location of a stop on the London Underground railway.
"It was written in good English, in note form ... apparently by the man who would construct the bomb," the report said.
The Observer says the language suggests the author was "British fundamentalist" - referring apparently to a Muslim fundamentalist from Britain in training in Kandahar.
It said most of the al-Qaida camps had been cleared out by U.S. Special Forces, but that "The Observer came across the padlocked compound ... when local Afghan residents led us to it."
The notebook was found in a room where papers had been tossed on a bonfire in the camp in Kandahar, the report said.
In addition to details of bomb construction, it lists how to behave in London to maintain his cover as part of a sleeper cell. Other documents found with it suggest it was written early this year, The Observer said.
It quoted Scotland Yard as saying its anti-terrorist officers would investigate.
The Independent on Sunday, another weekly, carried a similar report and said the only reference to timing was "Main Strategy: 1-2 weeks."
The Independent on Sunday said the handwritten notes covered 82 pages and were found by Daniel do Rosario, a journalist for the Portuguese newspaper Expresso, in a house at an al-Qaida training camp just outside Kandahar, captured last week.
The Observer did not say who found the notebook.
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