BRITAIN suffered its first casualties of war early today, hours after American and British forces launched their invasion of Iraq, assaulting President Saddam Hussein by land, sea and air.

Twelve Royal Marines and four Americans were killed when a US Marines Sea Knight helicopter crashed in Kuwait. It was the third American helicopter to come down yesterday, though the crews of the others escaped unharmed.

The soldiers had been taking part in what Washington promised would be an onslaught of unprecedented ferocity. American and British Marines had led the invading force as waves of Apache helicopter gunships swept across the Kuwaiti border, and infantry divisions targeted Iraqi troops in the South with cannon and rocket fire.

Royal Navy submarines fired Tomahawk cruise missiles at Baghdad, setting one of Saddam’s palaces and government buildings ablaze, and RAF Tornados flew bombing missions.

By the early hours, huge explosions lit up the sky close to the oil city of Basra — the allies’ first key objective — while American tanks closed in. Thirty fireballs rose above the flat desert plain after jets were heard flying overhead, apparently clearing the way for the US 7th Cavalry. The Royal Marines were earlier reported to have captured the key port of Umm Qasr, some 20 miles to the south.

But there were reports that the Iraqis had sabotaged three or four oil wells near Basra and that they were burning.

The allied invasion force was buoyed, however, by reports that Saddam and two of his sons had all been injured in the cruise missile strike on one of his palaces early yesterday.

Early in the day Donald Rumsfeld, the US Defence Secretary, had warned the Iraqi military to prepare itself for a war unlike any before. “What will follow will not be a repeat of any other conflict. It will be of a force and scope and scale beyond what has been seen before.” He urged Iraqi generals and troops to surrender or die with their leader.

Tony Blair addressed Britain in a television broadcast recorded before he left London for a European summit in Brussels. He said that British forces were engaged “from air, land, and sea” on a mission to remove Saddam from power and disarm Iraq. “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.

After the pre-dawn cruise missile strike aimed at Saddam and his top aides yesterday, American commanders had taken the conflict to a new level, ordering simultaneous attacks around the country.

In Baghdad, the Americans again fired cruise missiles against Republican Guard strongholds. The familiar red and white tracers streaked across the sky and the flash of explosions was seen on the horizon as Saddam’s main presidential complex blazed. Explosions could also be heard from the western side of the Tigris river, home to two more of the President’s palaces and the Intelligence headquarters. The Planning Ministry and the Deputy Prime Minister’s office were afire.

An intense artillery bombardment that lit up the skies over northern Kuwait had heralded the ground troops advance on to Iraqi soil. The US 1st Marine Expeditionary Force led the way across the demilitarised zone, and Iraqi troops who had been laying mines surrendered almost immediately.

At the same time the Royal Marines launched an aerial and amphibious assault on “Red Beach” at the head of the Gulf where the strategically important al-Faw peninsula meets the Shatt al-Arab waterway and the Iranian border. Hundreds of Britain’s elite soldiers swept into the peninsula while other British troops made beach landings and cleared mines.

American officials spoke of a “significant escalation” of the bombing campaign, but although more than a hundred cruise missiles were fired within a few hours, the initial stages stopped short of the relentless “shock and awe” attack the Pentagon had predicted. Officials suggested that the US was still striking against leadership targets to undermine confidence in Saddam.

Mr Rumsfeld sought to tighten the psychological screws on the Iraqi military to persuade them to give themselves up, saying: “The Iraqi soldiers and officers must ask themselves whether they want to die fighting for a doomed regime or do they want to survive, help the Iraqi people in the liberation of their country and play a role in a new, free Iraq.”

He said the US had indications that oil wells had been set alight. “It is a crime for that regime to be destroying the riches of the Iraqi people,” he said. Witnesses in Kuwait reported orange flames lighting up the sky near Basra.

President Bush, who signed the “execute order” authorising US forces into battle on Wednesday evening, said that the war may not be short. The conflict could be “longer and harder than some people have estimated it to be”, his spokesman, Ari Fleischer, said. Geoff Hoon, the Defence Secretary, delivered a similar message.

Saddam launched a propaganda fightback in two television appearances. The first, in which he spat defiance at “the criminal little Bush”, was designed to prove that the initial US strike had not killed him.

Washington refused to take the appearance at face value, embarking on a series of checks to see whether it had been pre-recorded. American officials said that they believed the person in the broadcast was Saddam — but one of the Iraqi leader’s former mistresses said that it was not him.

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