Bin Laden Planned Attacks On US Trains

Al Qaeda was planning an attack on the US rail network to mark the 10th anniversary of the September 11, 2001 attacks, US officials say.

The plot was apparently uncovered as US agencies went through information seized from Osama bin Laden's compound after the terrorist leader was killed in a raid by Navy Seals.

"We have no information of any imminent terrorist threat to the US rail sector, but wanted to make our partners aware of the alleged plotting," Department of Homeland Security spokesman Matthew Chandler said of an intelligence message sent on Thursday.

The idea - outlined in handwritten notes from the compound - was to tamper with a the track so that a train would fall into a valley or from a bridge, according to a joint FBI and Homeland Security bulletin.

However, there was no indication from the intelligence whether further plans were drawn up for the scheme or if steps were taken to carry it out.

Fox News cited a source as saying the plan was more aspirational than concrete and mentioned services in New York, Washington DC and Chicago.

The source said the evidence taken during the raid in Abbottabad, Pakistan on Monday considered the possibility of targeting a train travelling at 500mph, a speed that no locomotive in the US is capable of reaching.

Details of the alleged plot emrged as US President Barack Obama visited Ground Zero in New York to honour those killed in the September 11 attacks on the Twin Towers.

On Friday, President Obama will meet members of the Navy Seal team that killed bin Laden.

US TV newtwork NBC reported that much of the 40-minute operation was taken up retrieving computers, hard drives, mobile phones and other items that could offer valuable intelligence on al Qaeda and potential operations worldwide.

The material from bin Laden's hard drive was apparently transferred to CIA headquarters directly from the compound.

Since the raid, the Department of Homeland Security has reviewed security measures at potential terrorist targets, including transportation systems, adding more officers at airports and borders.

"We remain at a heightened state of vigilance," Mr Chandler said.

Officials have previously been concerned that al Qaeda or other groups might target the country's transport systems.

In 2008, US authorities warned of a possible al Qaeda threat to transit systems in and around New York City over the Thanksgiving holiday weekend.

Last year, an Afghan immigrant pleaded guilty in New York to plotting a suicide bombing campaign on Manhattan's subway system in what US authorities described as one of the most serious threats since the September 11 attacks.