Blast holes US warship

The gaping hole in the port side of the USS Cole

At least six American sailors have been killed in an explosion on a US Navy destroyer in the Yemeni port of Aden.

Eleven others are missing and 36 were wounded in the blast.

The explosion took place as the crew were refuelling the vessel, the USS Cole, which has been left badly gashed in one side. American investigators are on their way to the scene.

US President Bill Clinton said that if the explosion was, as it appeared, an act of terrorism, it was "despicable and cowardly".

"We will find out who was responsible and hold them accountable," he told reporters.

I have ordered our ships in the region to pull out of port and our land forces to increase their security.

President Clinton

US Secretary of State Madeleine Albright had earlier warned that "appropriate steps" would be taken if the blast turned out to have been the work of attackers.

Mr Clinton vowed that events would not force a change in US policy in the Middle East. But he added that US forces in the region had stepped up security measures.

A BBC correspondent in Cairo says American embassies in the region have already been the focus of angry demonstrations by crowds who believe Washington is siding unfairly with Israel in its conflict with the Palestinians.

No-one has claimed responsibility, however. The Yemeni authorities say the explosion was not deliberate.

Witnesses described it as being so powerful that buildings near the port shook.

FBI heads to Aden

US Attorney-General Janet Reno said the Federal Bureau of Investigation (FBI) had already dispatched local officials to the scene, and would be sending "investigators, explosive experts and an evidence response team".

US officials suspect foul play

The Pentagon has withdrawn an initial report that an inflatable raft, packed with high explosives, had rammed the USS Cole

But it says a small boat helping to moor the warship to a buoy positioned itself near the vessel. "I want to repeat that we do not know the cause [of the blast]," Defence Secretary William Cohen said.

But according to the US Navy, eyewitnesses saw two men on the smaller vessel stand up to attention just before it exploded.

I have no reason to think that this was anything but a senseless act of terrorism

US Navy Chief of Staff Vern Clark

The blast left a 20-40 foot gash in the port side of the destroyer, which is now listing badly.

Yemeni officials say the explosion took place inside the vessel. The Americans say otherwise.

"We know it occurred externally. An investigation is underway," the Fifth Fleet's Lieutenant Terrence Dudley told Reuters news agency.

Gulf mission

The USS Cole is an Arleigh Burke class guided missile destroyer with a crew of 350. It is armed with standard missiles and torpedoes.

The vessel was heading to the Gulf to join the US-led maritime interception operations in support of UN sanctions against Iraq.

It sailed through the Suez Canal on 9 October, down the Red Sea and had called into Aden for refuelling.

The US Fifth Fleet has more than a dozen ships, including an aircraft carrier, in the region.