One plan aimed to target a US rail route, the reports said, although no imminent threat was detected.

Officials are examining computers, DVDs and documents seized from the Abbottabad home where they believe Bin Laden hid for up to six years.

President Obama is due to meet some of the troops involved in the operation. He will hold private meetings on Friday at Fort Campbell, Kentucky, with at least some of the Navy Seals who took part in the raid.

On Thursday, the president visited Ground Zero, the site of the attack of 11 September 2001 in New York, laying a wreath in memory of the nearly 3,000 victims.

Bin Laden, who had been top of the US most wanted list since the attacks on New York and Washington in 2001, was killed by US special forces in northern Pakistan on Monday. The body of the al-Qaeda leader was then buried at sea from a US aircraft carrier.