America on edge

New security measures are being implemented across the US

		BBC News Online's Kevin Anderson in Washington

For the second time in three weeks, Attorney General John Ashcroft put the US on highest alert saying that the government had credible, but not specific information, that the nation could be the target of additional attacks in the coming week.

Some 18,000 law enforcement agencies were told to be especially vigilant in the coming week, and signs of the increased security are evident across the country.

But the detention of more than 1,000 people in the investigation of the attacks has civil liberties groups pressing the government for information and calling the secretive detentions undemocratic.

Country on guard

"We think it is very important since September 11 for America to remain on highest possible alert when we get this kind of information," said Tom Ridge, the director of Homeland Security.

Tom Ridge said that energy facilities had been contacted after the recent alert

The US continues to implement new security measures as it has since the attacks.

Boston Mayor Thomas Menino had sought to block liquid natural gas tankers from entering the city's harbour for fear that the ships and their highly flammable cargo might be used in an attack.

The Coast Guard had banned such shipments for nearly a month following the 11 September attacks but cleared the way for them to resume after a Lloyd's of London study said the shipments were safe.

The mayor insisted that the danger to the city was too high and that the Coast Guard's security plans were inadequate.

But a judge cleared the way for shipments to resume, and a tanker carrying almost 125 million litres of fuel came into Boston Harbour on Monday under heavy guard of helicopters and Coast Guard small boats.

Security has also been stepped up at sporting events including baseball's World Series

Such extra security measures have been taken at other US ports including San Francisco where sea marshals are boarding ships bound for the city's harbour.

The sea marshals are checking crewmembers against watch lists provided by the FBI and intelligence agencies.

The programme is the first of its kind, but it was seen as a priority in the densely populated area, with seven major bridges and several oil refineries and fuel depots and several other landmarks that would be prime targets for a terrorist attack.

'Zero tolerance' for security lapses

The US continues to try to tighten security at airports, but with uneven results, officials admit.

But Transportation Secretary Norman Mineta said that there would be "zero tolerance" of lapses.

The statement came a week after a passenger was able to carry a loaded handgun onto a flight at New Orleans airport. The passenger surrendered the weapon to a flight attendant and was not charged.

Security has been increased at airports, bus terminals and at train stations such

"We must crack down on these failures," he said, and said that security agents would re-screen passengers, shut down gates or entire concourses and delay flights if necessary to ensure security.

Congress is working on an airport security bill, but legislators are disagreeing on whether to make airport security workers federal employees or simply to provide federal oversight.

Information sought on detainees

Enhanced security and the investigation into the attacks has led to the detention of more than 1,000, the Justice Department announced on Monday, and a coalition of 21 civil liberties, human rights, immigration and public access groups have filed a request for the release of information about detainees.

Justice Department officials have been releasing the number of those detained but have provided little else in the way of information.

Officials said they are prohibited from releasing information in some cases, but civil liberties groups denounced the detentions as undemocratic.

One of the differences between democratic and totalitarian regimes is the use of secret arrests in repressive regimes, said Kate Martin, director of the Centre for National Security Studies, one of the groups involved in the petition for information about the detainees.

Ms Martin said: "We would agree that there obviously has to be some sort of secrecy, but the government hasn't made any argument that security requires the secret arrests of a thousand people.

"The secret detention of more than 800 people over the past few weeks is frighteningly close to the practice of 'disappearing' people in Latin America."