Osama bin Laden death confirmed in al-Qaida statement

Terror group posts message on extremist websites saying it will remain 'a curse chasing the Americans and their agents'

Pakistanis walk past graffiti translated as "long live Bin Laden" in Abbottabad. Photograph: Anjum Naveed/AP

Al-Qaida has confirmed the death of its leader, Osama bin Laden, and vowed vengeance, pledging in a statement posted on militant websites that his blood "will not be wasted".

In what is apparently the first official reaction from the militant Isamist group since Bin Laden was gunned down by US special forces troops who raided his hideout in the Pakistani town of Abbottabad, the group called on the people of Pakistan, "where Sheik Osama was killed", to rise up against their leaders.

The group would soon release an audio message from Bin Laden recorded a week before his death, said the statement, dated 3 May and signed by "the general leadership of al-Qaida". There was no independent confirmation that the message was authentic but it was posted on websites through which al-Qaida habitually issues statements.

It continued: "We stress that the blood of the holy warrior sheikh, Osama bin Laden, God bless him, is precious to us and to all Muslims and will not go in vain.

"We will remain, God willing, a curse chasing the Americans and their agents, following them outside and inside their countries. Soon, God willing, their happiness will turn to sadness, their blood will be mingled with their tears."

The statement came as US intelligence officials said Bin Laden had remained in close touch with the rest of the al-Qaida network from his safe house and had continued to plot potential terrorist attacks, including one against the US railway system.

The information reportedly comes from the initial analysis of files seized after he was killed. The US Navy Seals who shot Bin Laden in the early hours of Monday took away a mass of digital information on computers, hard drives and storage discs, as well as paper documents. An initial trawl through the files indicated Bin Laden was not a mere figurehead for the militant group but remained closely involved in nuts-and-bolts planning, according to various US reports.

As late as February last year, he seemingly took part in drawing up a previously unknown plot to attack a US commuter rail network, possibly on the 10th anniversary of the 9/11 attacks or another landmark date such as Christmas or new year, intelligence officials told US newspapers.

While the plot, apparently involving an attempt to derail a train by tampering with tracks, appeared to be only speculative, the seized documents seem to show Bin Laden was in regular contact with al-Qaida operatives from his house in Abbottabad. Before the raid, some analysts speculated that he had become an increasingly marginalised figure during his long presumed exile in remote tribal regions along the Afghan border.

Details have also emerged about the painstaking surveillance operation that preceded the raid on Bin Laden's hideout, in which a CIA team spied on the house for months from a property they rented nearby. The officers scanned the compound using telephoto lenses and infrared imaging equipment, and attempted to listen in on conversations inside, anonymous US officials told the New York Times.

The surveillance team regularly spotted a tall man walking through the compound's courtyard, although they never confirmed whether this was Bin Laden.

Such was the cost of the operation that the CIA requested tens of millions of dollars in extra funding from Congress in December last year, officials told the Washington Post.

Staff at an FBI lab at the marine corps base in Quantico, Virginia, have been poring over the trove of data as quickly as possible in case it describes any imminent attacks, but as yet there have been no specific alerts.

"He [Bin Laden] wasn't just a figurehead," one unnamed US official told the New York Times. "He continued to plot and plan, to come up with ideas about targets and to communicate those ideas to other senior al-Qaida leaders."

The department of homeland security has ordered additional security at airports and other transport hubs, and issued a precautionary note about the railway plot. "As of February 2010, al-Qaida was allegedly contemplating conducting an operation against trains at an unspecified location in the United States on the 10th anniversary of 11 September 2001," it said.

"As one option, al-Qaida 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."

A department spokesman told the Washington Post that the plot appeared speculative: "We have no information of any imminent terrorist threat to the US rail sector."

The documents may prove more fruitful in leading the US to other senior al-Qaida figures, including Ayman al-Zawahiri, al-Qaida's deputy leader. "We have lots of information on him," Mike Rogers, the Republican congressman who chairs the House intelligence committee, told the Washington Post. "I can't say it's imminent, but I do believe we're hot on the trail."

A day after laying a wreath to the victims of 11 September during a largely subdued visit to New York, Barack Obama is to travel to Fort Campbell, Kentucky, to meet the Seals who raided Bin Laden's compound.