Arrests, rumour and false alarms as manhunt spans the world

An increasingly jittery investigation into Tuesday's attacks on New York and Washington, and the network of suicide bombers behind them, spread around the world as police in at least eight countries swooped on members of Islamist groups suspected of ties to Osama bin Laden and his al-Qa'ida guerrilla group.

The frenzy of police activity included the arrest of six alleged activists in Belgium and the Netherlands, four of whom were picked up following an intelligence tip that they might be planning a strike against American targets in Europe.

In Italy, police reopened an investigation into the theft of a pilot's uniform, a badge and two US passports from American Airline employees last April. In Manila, American and Filipino authorities raided a hotel following reports that three men with Omani passports were seen videotaping the US Embassy across the street. A key arrest in the 1993 bombing of New York's World Trade Centre was made at the same hotel.

The hunt for associates of Mr bin Laden, named as the chief suspect in the attacks by the US Secretary of State, Colin Powell, continued in Germany, where one man was arrested earlier this week and a young woman taken in for questioning, and also spread to Mexico and France. In Britain, anti-terrorist officers and security service agents said they were tracking suspected members of al- Qa'ida but believed they had gone into hiding since Tuesday.

In the United States, meanwhile, there were increasing signs of panic as a flurry of arrests, airport closures and reports of possible new suicide hijacking attacks appeared to be the result of over-reaction or unreliable initial leads.

Ten people of Middle Eastern origin detained at John F Kennedy airport in New York on Thursday night – a threat taken seriously enough to prompt the closure of all airports in the area – were exonerated and released yesterday. Joseph Biden, chair of the Senate Foreign Relations Committee, explained that the panic that was prompted by their apprehension was the result of a series of coincidences. One belligerent man who insisted on being allowed on to a full plane turned out to be just that – belligerent and nothing more. A man in an American Airlines uniform turned out to be an American Airlines employee on his way to a Boeing conference.

Another man thought to be carrying a fake pilot's licence turned out to be a bona fide pilot carrying his brother's identity papers as well as his own. Mr Biden told reporters: "His brother happened to live in an apartment complex that was one in Boston where some of these people had actually been. Totally, totally coincidental."

There was also a melodramatic car chase in Staten Island that turned out to be a hunt for a phantom. In Florida, meanwhile, a flight engineer for Saudi Arabian Airlines, Adnan Bukhari, was cleared of suspicion after he passed a lie- detector test and evidence emerged that his identity might have been misappropriated by the hijackers. His name, along with that of his dead brother, was apparently picked up from a rental car left at an airport in Portland, Maine, and appeared to match another Bukhari questioned following the police raid in the Philippines.

There is growing evidence that the semi-autonomous cells that planned and executed Tuesday's attacks used a variety of subterfuges and decoys to fool investigators, including fake identities, false or altered passports, and even disguises. Historically, this has often been part of the modus operandi of guerrilla networks structured by semi-autonomous cells. The precise nationalities of the dead hijackers have yet to be pinned down, as have their relationships to one another. There are many similar names in circulation and reports of several sets of brothers, but these have not been established with any precision. It is not known how many of the hijackers knew each other, or whether they were aware of any more of the plot than their own specific part in it.

The latest intelligence from the Federal Bureau of Investigation, reported in yesterday's Los Angeles Times, suggests that up to 30 people were fully trained and ready to die for their cause. John Ashcroft, the Attorney General, has said 19 hijackers had actually gone into action, suggesting that there are another 12 at large, as well as a further 20-odd suspected accomplices.

Investigators are very worried about the possibility of another attack. In addition to the arrests in New York, two men were detained in Forth Worth, Texas, on Wednesday after they were found on an Amtrak train with box-cutting knives. The FBI has not ruled out the possibility that there was a plan to hijack a fifth plane at Dallas/Fort Worth airport.

New evidence has also emerged that Tuesday's attacks were five years or more in the planning. FBI agents investigating the records of flight schools in Florida attended by the hijackers have discovered that some of them were enrolled as early as 1997, and had probably submitted applications the previous year.

It also appeared that at least five of the 10 hijackers who boarded planes in Boston had claimed links to Saudi Arabian Airlines and had thus ducked some of the standard security clearance checks for Middle Easterners. Chuck Clapper, the owner of an air charter company in Lantana, Florida, told the Boston Globe that several Florida flying schools have contracts with Saudi Arabian Airlines that enable them to bypass much of the red tape involved in obtaining visas for their students. Asked if Arabs who seek to enter the United States need to seek State Department clearance, Mr Clapper said: "Saudis don't. Iranians do. Libyans do. But the Saudis are allies, so they don't." The Saudi cover may have enabled one of the dead hijackers, Mohamad Atta, to deflect attention from the fact that he was wanted in Israel in connection with a bus bombing in 1986. Had that fact come to light, he would almost certainly have been turned down for a visa.

The Saudi connection was picked by Laurence Eagleburger, the former Secretary of State, who said yesterday that the United States had been far too lenient on its erstwhile Gulf War ally and needed to get tough about possible indulgences by the Saudis of terrorist activity.

Such criticisms and recriminations are becoming more common as the days pass, as are knee-jerk responses to skin colour and nationality by US law enforcement officials supposedly banned from indulging in "racial profiling". One passenger at JFK, Mike Glass of Seattle, told The New York Times: "Anyone with dark skin or who spoke with an accent was taken aside and searched. And then they went to any male with too much facial hair."