Two American soldiers and two Iraqis have been killed in three separate attacks on US patrols in Iraq.
US troops on patrol are facing daily attacks
The first soldier was killed in an exchange of fire with two Iraqis in Baghdad, one of whom was shot dead, the US military said.
A second soldier was killed by a homemade explosive device in the north of the Iraqi capital.
In the town of Ramadi, 100 kilometres (60 miles) west of Baghdad, attackers fired rocket-propelled grenades at US vehicles, wounding four soldiers.
The Americans responded, killing one Iraqi and wounding another.
Three US soldiers have been killed in Baghdad in the past 24 hours, bringing to 29 the number of American soldiers killed in combat in Iraq since US President George W Bush declared major hostilities over on 1 May.
On Sunday, a US soldier died of his wounds after being shot in Baghdad.
The soldier was guarding the university campus in the centre of the city when he was shot in the head, a US military spokeswoman said.
A young British freelance journalist was killed in a similar style on Saturday, when he was shot in the head outside a Baghdad museum. He was apparently carrying nothing to indicate that he was a reporter.
Tensions have been high in the town of Ramadi since an explosion on Saturday killed seven Iraqi police recruits as they graduated from a US-taught training course. Dozens
of Iraqis were injured.
The US military blamed the attack on Saddam Hussein loyalists.
Ramadi is a mainly Sunni Muslim region which has a history of support for Saddam Hussein.
The US official in charge of setting up Iraq's police is preparing to unveil a reward scheme for information relating to the killing of coalition forces or Iraqi police officers.
Bernard Kerik, a former New York police chief, told the BBC the minimum reward would be $2,500.
The US has offered a $25m reward for information leading to the capture of ousted Iraqi President Saddam Hussein.
Last week, Al-Jazeera television broadcast an audio tape purporting to be from Saddam Hussein, in which the speaker urged Iraqis to resist the US-led forces in Iraq.
The US has launched a series of military operations to hunt down Iraqi fighters since May.
The latest, Operation Sidewinder, ended on Sunday after a week in which troops in central Iraq arrested 282 people and seized a variety of weapons including 96 AK-47 rifles, three heavy machine guns, 217 rocket-propelled grenades and 33 grenades.
US Central Command says its troops will continue to conduct active patrols.
US Army Major William Thurmond said they were determined to stop the attacks.
"There's no place for that in any civilised part of the world," he said. "We'll find them. We'll attack them. And if necessary, we'll kill them."