Insurgents ambushed two U.S. military patrols north of Baghdad on Sunday in separate attacks that killed three U.S. soldiers and an Iraqi civilian.

A roadside bomb attack in the afternoon in Samarra, 70 miles north of Baghdad, killed two soldiers and wounded three others, the military said.

An attack on a U.S. convoy in Baiji, 110 miles northwest of Baghdad, began Sunday morning when a roadside bomb exploded, the military said. Occupants of a vehicle then raced toward the convoy, firing at the soldiers, who shot back and killed the driver, the military said. A soldier and a civilian traveling behind the patrol were killed. A second soldier was injured and evacuated. Thick black smoke poured over the area from an oil tanker set on fire in the attack.

The deaths came a day after four U.S. Marines were killed in a vehicle accident near Fallujah, west of Baghdad. More than 875 U.S. military personnel have died since the U.S. invasion of Iraq.

[Meanwhile, insurgents holding a Filipino truck driver hostage in Iraq gave the Philippines another 48 hours on Monday to agree to withdraw its 51 troops before they killed him, a minister said in Manila, according to the Reuters news agency.

"I think there are now new signals that the extension of the deadline has been given another 48-hour life," Labor Secretary Patricia Santo Tomas said in a television interview, Reuters reported.]

The Philippine government on Sunday rejected the ultimatum.

Militants from a group calling itself the Islamic Army of Iraq -- Khaled bin Al-Waleed Brigade had earlier given the Philippines a Sunday night deadline to agree to withdraw its troops by July 20, a month ahead of their scheduled departure.

The wife and brother of the truck driver, Angelo de la Cruz, were heading to Baghdad, Foreign Secretary Delia Albert said.

A deadline for two other hostages, Bulgarian truck drivers held by a separate group demanding the release of all Iraqi detainees, expired Saturday morning. Bulgarian Foreign Minister Solomon Pasi said Sunday he had unconfirmed information that the two were alive.

In another development, Iraq's national security adviser, Mowaffaq Rubaie, said the country would honor the nuclear Non-Proliferation Treaty and international agreements banning the use of chemical and biological weapons.