Americans urged to stay vigilant

Security is tight around the US embassy in Bangkok

Americans have been warned to be extra vigilant for any new attacks as the US launched a second day of air strikes on Afghanistan.

With law enforcement agencies on the highest state of alert across America, US Attorney General John Ashcroft said extra physical security was in place in and around US nuclear facilities, and at chemical and petrochemical plants.

"We are taking strong precautions and other appropriate steps to protect the American people while we win this war," said Mr Ashcroft.

Megawati has expressed support for US anti-terror aims

He said the FBI was treating a second case of anthrax in Florida as a possible criminal investigation, saying officials could not rule out the possibility the outbreak was the result of a biological warfare attack.

The warning came as the new head of the US Office of Homeland Security, Pennsylvania Governor Tom Ridge, was sworn in. The body was set up in response to the 11 September attacks.

Americans abroad have also been warned about the danger of retaliatory action.

US citizens in Indonesia - the most populous Muslim nation - have been told to stay indoors if possible, and to be prepared for possible evacuation.

Threat from Islamic group

Indonesian President Megawati Sukarnoputri has expressed support for the United States "war against terrorism". But correspondents say anti-American sentiment has grown since Washington set its sights on the Muslim leadership of Afghanistan following the suicide attacks.

The radical Islamic Defenders Front has threatened to hunt down foreigners, and has called for a siege of the US embassy in Jakarta, the Indonesian capital.

Security has also been tightened outside the US embassy in Kuala Lumpur, the capital of Malaysia - which also has a Muslim majority - and elsewhere.

Middle East fears

US and British citizens in the Middle East are being advised to keep a low profile amid fears of retaliation for Sunday's air strikes.

Most Arab governments have kept silent about the strikes. But many among their populations will have watched Osama Bin Laden's pre-recorded call to arms via the Qatari-based television channel al-Jazeera.

A major UK military exercise is under way in Oman

In Oman, where 23,000 British troops are currently on exercise, extra security precautions are being taken for the British community.

Security has been tightened at the UK embassy and a 24-hour consular advice line set up for the estimated 6,500 UK expatriates living in this Gulf Arab state.

The embassy has also advised two British schools to remain closed for the next day or two while it assesses any possible risks to British citizens.

UK role

The BBC's Middle East correspondent Frank Gardner says such precautions could be unnecessary in Oman - a peaceful, hospitable country ruled by a pro-Western monarch. But many young Omanis oppose Western military action against a fellow Muslim state.

They will now be digesting the news that three British submarines were involved in the strikes against Taleban positions, operating not far from Oman in international waters.

Elsewhere in the Gulf, westerners were already on a high state of alert even before the attacks took place in Afghanistan.

Although violence is rare in this part of the Middle East, nerves have been jangled by a bomb attack on Saturday in Saudi Arabia.

One American was killed along with another man and four people were injured, including a Briton.