FBI round-up after 11 September 'foiled al-Qa'ida cell's attack plans'

An American cell of the al-Qa'ida network was close to launching another terror attack in the aftermath of 11 September but was disrupted by the FBI, a news report claimed yesterday.

The cell was planning to hit a target in Washington – possibly the Capitol building, which houses Congress – but its members were forced to go to ground or flee the country after an FBI sweep.

The claim – in the latest edition of Newsweek magazine – comes against a backdrop of genuine concern in the country about the possibility of another attack, a worry that has increased as America has continued its military campaign in Afghanistan.

The FBI has issued three separate security alerts since 11 September after receiving "credible" intelligence that there might be other attacks. On each of these occasions – the most recent issued two weeks ago – the FBI said the alert was general rather than specific and that there was no information about possible targets. It is believed, however, that the hijacked United Airlines flight 93, which crashed in rural Pennsylvania, may have been intended to strike the Capitol before the hijackers were tackled by some of the passengers.

The magazine quotes unnamed security sources within America, which say the disrupted post-11 September attack was being planned by a so-called al-Qa'ida sleeper cell. This plan was allegedly disrupted by the FBI's sweep of visa violators and other suspects of Middle Eastern background, which the magazine said picked up members of an al-Qa'ida support group. This group was responsible for providing information and equipment for those members who would actually carry out the attack.

As a result of the support group being picked up, the other members were forced to go to ground.

The magazine said it was not clear whether they were still in the country. While the authorities believed that they had disrupted the support cell, investigators had not been able to identify the plotters from among the hundreds of people detained by the FBI and were not even sure they were still in custody, Newsweek said.

There was no official comment yesterday on these reports. John Ashcroft, the American attorney general, hassaid that a number of the 650 or more people who are facing criminal or immigration charges after being picked up by the anti-terror sweep were al-Qa'ida members.

Paul Wolfowitz, the deputy secretary of defence, said yesterday that despite the efforts of law enforcement agencies, they believed that al-Qa'ida members were still at large within the country.

The magazine also claimed that Osama bin Laden ensured his network was protected by plying his Taliban hosts with money and gifts. "He was always handing out $50,000 to this commander, or $10,000 to that commander," said Mullah Alhaj Khaksar, a senior Taliban defector. "And cars – Afghans love cars. He would get 20 or 30 cars and bring them in from Kandahar as a present just before an offensive."

Western intelligence agencies have estimated that Mr bin Laden funnelled as much as $100m a year to the Taliban – twice Afghanistan's official annual budget.