THE war against Iraq claimed its first British casualties early today when a helicopter crashed in the Kuwaiti desert.

The tragedy occurred as American and British forces drove into Iraq, attacking by "air, land and sea".

British Royal Marines were said to have stormed ashore with an aerial and sea assault on the strategically vital al-Faw peninsula, at the head of the Gulf and near the southern Iraqi city of Basra.

It is reported that eight Royal Marines from 3 Commando Brigade and four US Marines were killed when a twin-engined Sea Knight helicopter crashed in Kuwait at about 3am.

The Pentagon is investigating the crash but there was no indication that the helicopter was shot down. It is believed that it was an accident, possibly caused by a mechanical fault.

The tragedy occurred as American and British troops pushed further into southern Iraq.

British Foreign Secretary Jack Straw expressed the government's condolences to the families of those killed in the crash.

He said: "Our hearts and prayers go out to those who perished and their loved ones. This is a very early stage of the military campaign.

"We hope and pray that the campaign will be over quickly."

American forces, including the 3rd Infantry Division accompanied by a large convoy of vehicles, were advancing through the desert, possibly with the intention of securing the southern Iraqi oil field, where last night wells were said to have been set alight.

British forces were reported to have taken the vital sea port of Umm Qasr, as well as oil pumping equipment in the area. And there have been reports of a US flag being raised over the port.

But Defence Secretary Geoff Hoon said today that British forces were meeting "stern resistance" in the area of Umm Qasr.

There were conflicting reports about the amount of resistance being encountered by the invading forces. Some suggested that they were making good progress with little interference, but others mentioned counter-strikes by the Iraqis, including attacks using anti-tank missiles.

During the night cruise missile attacks were again carried out on Baghdad, although the attacks were said to have gone on for only about 15 minutes. There were reports of explosions in Basra and Mosul. An air raid warning was also heard in Kuwait City before 7am today.

Saddam Hussein remained defiant, saying his forces would never surrender.

Meanwhile Tony Blair told the nation last night that its forces were engaged by "air, land and sea".

He said that while he knew the war had produced deep divisions, he knew British people would unite to send the Armed Forces their hopes and prayers.

He said the world was facing a new threat from "brutal states" armed with weapons of mass destruction, and from extreme terrorists. His fear, partly based on intelligence he received, was if the two came together.

"As so often before, on the courage and determination of British men and women serving our country, the fate of many nations rests," he said.