The FBI has joined Pakistani investigators sifting through the wreckage of Friday's bomb attack on the US consulate in Karachi that killed at least 11 people and injured 40.

Police say some suspects have been detained for questioning, but no arrests have been made.

News of the blast was carried in Saturday's papers

A previously unknown group called al-Qanoon ("The Law") said it carried out the attack but there has been no confirmation of the claim.

Witnesses said FBI officials visited the crime scene on Saturday.

"They took photographs and made a video of surrounding areas and the spot of the bomb attack," one witness told Reuters news agency.

President George W Bush has described the bombers as "radical killers" who had no respect for individual life, and warned that the US would not be intimidated by the attack.

The continuing attacks on foreigners, along with the threat of war between India and Pakistan, have led the US and other countries to call for all nationals to leave the country unless their work was essential.

The US has closed its diplomatic missions in Pakistan as well as the American Center in Islamabad. It is not clear when they will re-open.

Pakistan's military spokesman, General Rashid Qureshi, has said the attackers are trying to create a mass exodus of foreigners to put pressure on the government.

But he said there was no major threat and no need for them to leave Pakistan.

Forceful blast

The dead, who were all Pakistanis, included five women and four policemen guarding the heavily fortified building.

The explosion, which blew a gaping hole in the mission's perimeter wall, scattered cars across the road, smashed windows and brought down power lines.

It was the second in Karachi in a matter of weeks, after a bomb attack outside the Sheraton hotel last month killed 11 French nationals and three Pakistanis.

It came a day after US Defence Secretary Donald Rumsfeld had talks in Islamabad with Pakistan's President Pervez Musharraf on curbing extremism in the region.

India 'not ruled out'

Pakistan's information minister said the involvement of the Indian intelligence services could not be ruled out.

India has condemned the attack.

Police had said the bomb was concealed in a white vehicle that the driver had crashed into a police kiosk at the southern end of the consulate.

But investigators now say the explosion may have been detonated by a remote-controlled device.