Osama was planning attacks on US railways, big cities:

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A treasure trove of materials taken from Osama bin Laden's hideout in Pakistan indicates that Al Qaeda was mulling attacks on key US cities and railways timed to significant dates, according to US officials.

Material recovered from the raid on bin Laden's Abbottabad hideout indicated that in February 2010, Al Qaeda members discussed a plan to derail trains in the US on the 10th anniversary of the Sep 11, 2001 attacks by placing obstructions on tracks, multiple media reports said.

Other material gathered from the site also suggests that Al Qaeda was particularly interested in striking Washington, New York, Los Angeles and Chicago, the CNN said.

US authorities have found that Al Qaeda appears especially interested in striking on significant dates like America's July 4 Independence Day, Christmas and the opening day of the United Nations.

As a precaution, the Department of Homeland Security on Thursday sent out an alert advising federal, state and local agencies about the new evidence of a possible rail plot.

"As one option, Al Qaeda was looking into trying to tip a train by tampering with the rails so that the train would fall off the track at either a valley or a bridge," said the DHS advisory.

After reviewing computer files and seized documents, American intelligence analysts have concluded that bin Laden played a direct role for years in plotting terror attacks from his Abbottabad hide-out, The New York Times said citing US officials.

The materials, along with others reviewed in the intelligence cache, have given intelligence officials a much richer picture of the Qaeda founder's leadership of the network as he tried to elude a global dragnet, it said.

"He wasn't just a figurehead," the Times cited one American official as saying. "He continued to plot and plan, to come up with ideas about targets, and to communicate those ideas to other senior Qaeda leaders."

The fact that Bin Laden was found not in Pakistan's rugged tribal areas but on the outskirts of an affluent town less than an hour's drive from the capital, Islamabad, has prompted a rethinking of the widespread notion that he had little control over the rest of Al Qaeda, the daily said.

Other gleanings from the roughly 100 pieces of computer gear seized on Sunday included possible leads on the whereabouts of other senior Al Qaeda leaders, the Washington Post reported.

While intelligence officials declined to comment on specific tips, a key congressional leader briefed on the findings suggested that the search for Al Qaeda's No. 2 leader was in a newly active phase, it said.

The task of identifying and exploiting intelligence tips has been assigned extraordinary urgency, since the raid likely alerted top Al Qaeda figures that their safe houses and plans may have been compromised, the Post said citing a US official.