Baghdad, Iraq ? Attacks against the American occupying force in Iraq escalated Monday as two soldiers were killed and four were wounded in two separate ambushes on military convoys in one of the most violent days since the end of the war.

Attackers fired rocket-propelled grenades, heavy machine guns and small arms at an eight-vehicle supply convoy in what military officials described as an ambush at 6:15 a.m. near Hadithah, 120 miles northwest of Baghdad, killing one soldier from the 3rd Armored Cavalry Regiment and injuring another.

Hours later, one soldier was killed and three wounded when a Humvee near Baghdad International Airport was either hit by, or ran over, a landmine or other type of explosive that had apparently been hurled at it, military officials said.

Three other U.S. soldiers died in separate incidents Monday, with all three fatalities believed to be accidental.

The latest assaults on U.S. troops in Central Iraq, the third in the past week, occurred as the 1st Armored Division arrived to join the 3rd Infantry Division to double patrols in the Iraqi capital and as officials with the Pentagon’s Office of Reconstruction and Humanitarian Assistance labored to show progress in public safety and acceptance of the American presence by the Iraqi people.

U.S. military officials described the incidents as aberrations that occurred amid a visible increase in American soldiers, who have left their intimidating Bradleys behind to patrol in Humvees and, for the first time, on foot.

“It could be an attempt to disrupt the transition,” said Lt. Col. Scott Rutter, of the 3rd Infantry Division’s 1st Brigade, which commands the unit attacked near the airport. “I honestly think order still exists in Baghdad.”

Yet support for the attackers was evident among the local residents gathered at a military cordon 100 yards away. As teenagers chanted “boom boom” and “bye bye” to American soldiers near the site of the Humvee attack, local residents described the assaults as a guerrilla resistance against the occupation by supporters of the former Baathist regime of Saddam Hussein.

“This is only the beginning,” said a middle-aged man near the attack, who refused to give his name. He claimed two former military officers plotted the attack on the Humvee out of revenge for U.S. policies that disbanded the Iraqi army and purged government posts of senior members of the Baath Party. “These people declared holy war against the American people.”

Antipathy has intensified since a series of deadly skirmishes in Central Iraq strongholds of the former regime such as Falloujah. U.S. soldiers killed two Iraqis in the village last week after a Bradley Fighting Vehicle on patrol was ambushed with a rocket-propelled grenade.

U.S. officials in Baghdad acknowledged lingering concerns over order and a growing hostility toward the American presence, but complained that the coalition’s progress has gone underappreciated because of unreasonably high expectations for a return to normalcy just six weeks after the war’s end.

Americans and Iraqis alike need to be patient, said Rep. Duncan Hunter, R-Calif., the chairman of the House Armed Services Committee, who on Monday led the first congressional delegation to Baghdad since the war ended.

L. Paul Bremer, the U.S. civil administrator who is running Iraq, outlined on Monday what he described as “magnificent” progress — including formation of a “de-Baathification” committee to advise him on how to eliminate the ruling party of the former regime and redistribute its assets.

U.S. forces arrived quickly and in force in response to both attacks Monday, but no assailants were captured. The names of the casualties were withheld pending notification of relatives.