Terror alert sparks airport closures

Gatwick and Stansted are sealed off / Suspect found with grenade / Three arrested

The British public was urged to be "alert but not alarmed" last night after a series of security operations including the closure of Gatwick airport and arrests by anti-terror police.

David Blunkett, the Home Secretary, was forced to appeal for calm as a man on a flight into Gatwick was arrested for carrying a live hand-grenade and two other suspects were detained near Heathrow.

Rising public anxiety was fuelled when Stansted airport said it would close its access road to the public after a "non-specific" threat reported by the intelligence services.

More than 100 flights were affected at Gatwick and hundreds of passengers at the airport's North Terminal were left stranded and angry by the six-hour delay. It was eventually reopened shortly before 8pm.

Mr Blunkett said there was a "real and serious" threat to the UK from al-Qa'ida, as MI5 made clear that extra police and troops had been drafted into London specifically to thwart the threat of a surface-to-air missile attack on an aeroplane.

Amid continuing criticism that the Government's handling of events had been confused, tanks were withdrawn from view at Heathrow, although security remained tight.

Downing Street and the Home Office called on the public not to "overreact" and "do the terrorists' work for them" by cancelling flights and holidays.

Mr Blunkett clearly resented having to make a Commons statement on the troop deployment and warned that it was more dangerous to provide a "running public commentary" on every new threat.

A Venezuelan man, 37, on a British Airways flight from Bogota to Gatwick was arrested under the Terrorism Act after police found a live grenade in his luggage. Part of the airport's north terminal was evacuated during the five-hour alert and all departure flights halted.

Mr Blunkett said the arrest underlined the government case for vigilance. "First, it reinforces that we really do have a problem, as people have been saying we are making it all up. Second, it means that our security services are on the ball." He added: "We know al-Qa'ida will try to inflict loss of human life and damage upon us."

But in a clear indication of the confusion at the Home Office, Mr Blunkett's official spokesman tried to reassure travellers that the arrest was not likely to be linked to Osama bin Laden. "It is not uncommon for people in airports to be discovered with some form of weaponry. It doesn't mean they are all al-Qa'ida terrorists. People should not jump to conclusions about this incident," he said.

As armed police remained on high alert at airports in Manchester, Birmingham and Liverpool, authorities at Stansted said the access road to its terminal building would be closed to the public from today.

Worldwide indications of heightened tension were in evidence as National Guardsmen stood watch at New York City's Grand Central rail Terminal.

Mr Blunkett told MPs: "The public must be given the information needed to protect themselves and others. That is what we have done. But we must also avoid frightening people unnecessarily or causing the kind of economic and social damage that does the work of the terrorists for them. The public must be alert but not alarmed."

Security at Heathrow, the country's busiest airport, was still high, with many soldiers and extra police on duty. Light tanks had been stationed by the main entrance and terminal buildings and were expected to patrol the airport perimeter for weeks to come.

The Ministry of Defence (MoD) said a military aircraft had been patrolling the skies above London. An MoD spokesman said: "We can confirm that there was an Nimrod supporting the police operation. It's a communication aircraft."

Ministers and senior police officers admitted yesterday that they had considered closing Heathrow over fears of an attack but instead decided to use the Army to create a ring of steel around it. About 1,700 extra police officers were at Heathrow and other London sites and security was also beefed up at Manchester airport, including spot checks by armed officers.

Meetings of Cobra, the Cabinet Office's civil contingencies committee, have been called and police warned there could be more operations involving the Army.

Security experts have speculated that the Heathrow alert might be based on fears that terrorists could be on the loose with a shoulder-held missile launcher similar to that used in an unsuccessful al-Qa'ida attack on an Israeli passenger jet in Kenya last year. Heathrow is one of two airports in the UK used by the Israeli airline El Al. The other is Stansted.