A UK marine has been killed in an ambush during operations in southern Iraq.
The Faw peninsula was one of the first coalition targets of the war
Several other troops were injured in what was reported to be an attack on a river patrol on the Faw peninsula.
It came as UK forces further north launched a massive offensive against Iraqi forces near the city of Basra.
Iraqi fighters in the village of Abu al-Qassib had put up the hardest resistance the Royal Marines have seen so far.
They said five senior Iraqi officers, including a general, had been captured and a "strongpoint" overrun.
Back in the UK, Defence Secretary Geoff Hoon told the BBC that troops in Iraq would be replaced if the conflict continued for months.
The family of the marine killed on Sunday have been informed, the Ministry of Defence said.
It takes the number of UK personnel killed since the start of the war to 24.
The death came when a launch carrying troops working near a vital pontoon bridge on a waterway at the top of the Faw peninsula came under a grenade and gunfire attack
According to a reporter with the unit, three Royal Marines were initially injured in the attack.
Another marine was thrown into the river and a comrade dived in to rescue him.
An officer left on board reportedly regained control of the craft and dragged his comrades to safety.
The corporal, whose actions have been praised by his officers, then drove the craft out of the area and the injured, one surviving a direct hit to his flak jacket, were helicoptered out to a field hospital.
The seriously injured marine later died from his injuries.
The BBC's Kylie Morris said the Army Air Corps responded to the attack by sending Lynx helicopters to destroy three Iraqi boats on the channel.
Three coalition boats have been patrolling the waterway to give protection to the key port of Umm Qasr.
The fighting near Basra was centred on the village of Abu al-Qassib after it was targeted in a raid by 3 Commando.
High ranking captives
Our correspondent said the village is described as having been a centre of resistance and possible source of counter-attacks by Iraqi tanks launched over the past few days.
Dozens of soldiers were made prisoners-of-war and have been moved to Umm Qasr, where the British now hold as many as 3,000 PoWs.
The offensive around Basra was described by one British officer as "the marines' largest operation of the war so far".
Military spokesman Group Captain Al Lockwood said there had been "aggressive patrolling" by the British military in and out of Basra.
He said: "A Republican Guard colonel has been killed and we have several other high-ranking prisoners."
He said military officials understood that throughout Iraq elements like this senior officer had been sent to strengthen Baath Party officers and paramilitary forces.
"But what has become obvious in the last day or so, is that in Basra and other towns the local population are now beginning to trust us, they are talking to us and giving us valuable information," he said.
Fuel supply struck
In the Rumaila oil fields, another Baathist official has been captured by British forces as they continue their campaign to destroy Saddam Hussein's Baath party in Basra, said BBC correspondent Kylie Morris.
Foreign Office Minister Mike O'Brien told the BBC the campaign in Iraq was "on track" and following consultations with military generals the government had no plans "at this point" to increase British forces in the Gulf.
But Mr Hoon said the commitment of 45,000 British troops would have to be reviewed once the conflict moved to a "different" phase.
The defence secretary said he had absolute confidence in the coalition's military strategy and it was "not possible" it would lose the war or be forced into a stalemate.