Two US soldiers were wounded when a military convoy came under attack on a highway between the flashpoint towns of Ramadi and Fallujah, west of Baghdad, witnesses said.
In a separate incident three landmines blew up under a US convoy of six military vehicles passing through the al-Falahat area west of Fallujah, destroying a Hummer vehicle and wounding at least two more American soldiers, bystanders told Aljazeera.
US forces arrested three Iraqis in the nearest village followed the incident, witnesses said.
The US Army did not immediately confirm either incident.
Near Balad, north of Baghdad, two soldiers were wounded when their convoy came under rocket-propelled grenade fire, according to Lieutenant Colonel Bill MacDonald of the Fourth Infantry Division.
"Three Iraqi civilians were also wounded by the attack. The two soldiers were evacuated for medical treatment, they are in stable condition. The Iraqis were treated on the site and released," he said.
At least 60 American soldiers and seven British troops have been killed in guerrilla-style attacks since the White House declared major combat operations in Iraq over on 1 May.
The attacks came during a day of demonstrations in Baghdad that further highlighted the mounting resentment among the Iraqi people towards the occupying forces.
"We will not be responsible for what will happen to the Americans if they enter Sadr City again."
Sheikh Abdul Hadi al-Daraji
Ten thousand people gathered in the impoverished Sadr City district for special weekly prayers to denounce a perceived US army assault on their cherished faith.
"They were not just attacking a flag, they were attacking all of Islam," Sheikh Abdul Hadi al-Daraji told his congregation.
Daraji rejected a US apology for the incident in which an Iraqi was killed on Wednesday in clashes sparked when American troops in a helicopter removed a religious flag from a communications tower in the Shia suburb previously known as Saddam City.
And he warned, "We will not be responsible for what will happen to the Americans if they enter Sadr City again."
The US army rejected the threats, saying patrols in the powder keg area would continue.
"We still have a security policy that needs to go on in that area," said army spokesman Colonel Guy Shields.
Elsewhere, members of the Iraqi Association for Democracy called upon the US civil administration in Baghdad to set up a comprehensive social security system to counter unemployment and poverty.
In a demonstration before the Presidential palace in Baghdad, activists called for the security, stability and the restoration of a regular electricity supply.
The protestors included a number of disabled people who demanded the US civil administration offer them job opportunities.
On Thursday, US forces in the Al-Sidiya area, south Baghdad, distributed leaflets threatening to block services and humanitarian aid if local people refused to identify resistance fighters, Aljazeera’s correspondent reported.
On an average two occupation soldiers a day have died in Iraq since the start of the war.
Basic services such as drinking water and electricity have yet to be restored to pre-war levels in the wrecked country, even though more than three months have passed since President Bush declared an end to major combat operations.
On average two occupation soldiers a day have died in Iraq since the start of the war on 20 March and a total of about 830 have been injured.
Over 6,000 Iraqi civilians have been killed in the recent conflict, according to media reports.
Despite US hopes that the killing of Saddam Hussein’s much-feared sons Uday and Qusay on 22 July would quell opposition, 35 occupation soldiers have since met their deaths in combat.
At least another 60 more have died in what the US calls "non-combat" incidents since 1 May, when President Bush declared major combat operations over. These include accidents and suicides.