Five U.S. soldiers were killed Monday when their patrol was hit by a roadside bomb and then came under small arms fire in the northern Iraqi city of Mosul, the U.S. military said.
Iraqi army and police also reported fighting had broken out in the Haysuma neighborhood, a known al-Qaida stronghold in eastern Mosul, Iraq's third-largest city, which is 240 miles north of Baghdad.
On Sunday, Iraqi security officials said that Iraqi tanks and helicopters were being sent to Mosul for a big offensive against militants from al-Qaida in Iraq.
Prime Minister Nouri al-Maliki said Friday that Iraqi forces were preparing for a "decisive" offensive against al-Qaida in Iraq to push the Sunni Islamist militants out of their last major urban stronghold.
U.S. military officials Sunday said their own operations around Iraq's third largest city were continuing.
"As it stands ... we are executing day-to-day operations in support of Operation Phantom Phoenix," said Maj. Gary Dangerfield, spokesman for the 3d Armored Cavalry Regiment in Mosul, referring to a nationwide offensive launched this month.
"We are not in a position to validate the prime minister's future plans," he said.
U.S. military commanders say al-Qaida in Iraq, blamed for most serious bombings in Iraq, has regrouped in northern provinces after being squeezed out of the western province of Anbar and from around Baghdad during security crackdowns last year.
Military spokesman Rear Adm. Greg Smith said al-Qaida in Iraq had used two 15-year-old boys to carry out suicide bombings in the past week, one in Mosul and the other in Tikrit.
"We're not sure if one of these children even knew he was being used to deliver a bomb," Smith said.
"These attacks were perpetrated at a funeral, a solemn religious ceremony, and at a school, a place that should be a safe haven for the young," Smith told a news conference.
The U.S. military has some 3,000 troops in and around Mosul, capital of Nineveh province.
Huge blast
Maliki made his announcement after a blast blamed on al-Qaida in Iraq killed 40 people and wounded 220 in Mosul on Wednesday. The explosion was in an unoccupied building that officials said was used by al-Qaida in Iraq to store weapons and explosives.
Defense Ministry spokesman Mohammed al-Askari said tanks, armored vehicles and helicopters were being sent to Mosul for an offensive "very soon."
Askari said the defense minister, Gen. Abdel Qader Jassim, had visited Mosul to meet military commanders. The Interior Ministry said the Mosul push would include 3,000 extra police.
The U.S. military calls al-Qaida in Iraq the biggest threat to Iraq's security.
Despite frequent violence in northern Iraq, overall attacks have fallen sharply across the country, with the number of attacks down 60 percent since last June.
That has been attributed to an extra 30,000 U.S. troops sent to Iraq last year, the growth of mainly Sunni Arab neighborhood security units and a cease-fire by the feared Mahdi Army militia of Shiite cleric Muqtada al-Sadr.
But U.S. and Iraqi forces insisted they would continue to hunt down so-called rogue fighters who ignored the order. Al-Sadr’s followers claim that is a pretext to crack down on their movement.