Updated

Five American soldiers were killed Monday by a roadside bomb in the northern city of Mosul, described as one of Al Qaeda in Iraq's last strongholds, just days after a house explosion and suicide attack killed as many as 60 people there.

Insurgents in a nearby mosque opened fire on other soldiers in the patrol after the roadside bombing, prompting a fierce gunbattle as U.S. and Iraqi troops secured the area, the military said. Iraqi soldiers entered the mosque but the gunmen had already fled, according to the statement.

Iraqi army reinforcements have moved into position near the city, 225 miles northwest of Baghdad, ahead of a planned offensive announced by Iraqi Prime Minister Nouri al-Maliki.

Monday's deaths raised to at least 36 the number of American troop deaths reported this month, an increase from the 23 recorded in December in one of the lowest monthly totals since the war started in March 2003.

Iraqi police in Mosul, the capital of Ninevah province, reported clashes between U.S.-Iraqi forces and gunmen in a middle-class Sunni neighborhood believed to be an insurgent stronghold.

An officer, speaking on condition of anonymity because he was not authorized to release the information, said three civilians were wounded and helicopters had bombarded buildings in the southeastern Sumar neighborhood, which has seen frequent attacks on U.S. and Iraqi forces that have led to a series of raids.

"The insurgents are willing to desecrate a place of worship by using it to attack soldiers to further their agenda," said Maj. Peggy Kageleiry, a U.S. military spokeswoman in northern Iraq.

U.S. commanders describe Mosul as the last major urban center with a significant Al Qaeda presence since the terror network has been driven from its strongholds in the capital and Anbar province.

The U.S. military has said Iraqi security forces will take the lead in Mosul — a major test of Washington's plan to, at an undetermined date, shrink the American force and leave it as backup for Iraqi security forces.

The Iraqi Red Crescent Organization, meanwhile, gave a higher death toll than Iraqi officials from Wednesday's devastating house explosion. The U.S. military said the cause of the blast has yet to be determined, although Iraqi officials were quick to blame Al Qaeda.

Bolstering that claim, a suicide attacker killed a top police official and two other officers as they toured the wreckage the next day.

The relief organization said more than 60 people were killed and 280 wounded based on estimates from relatives who buried victims without officially registering them. Iraqi officials in Mosul maintain that nearly 40 were killed and more than 200 wounded.

The U.S.-led security crackdown, along with a Sunni revolt against Al Qaeda in Iraq and a cease-fire order by radical Shiite cleric Muqtada al-Sadr have been credited with a dramatic drop in attacks in the capital.

However, influential members of al-Sadr's movement said Monday they have urged the anti-U.S. Shiite cleric to follow through with threats not to extend the cease-fire when it expires next month, a move that could jeopardize the recent security gains.

The Sadrists are angry over the insistence of U.S. and Iraqi forces on continuing to hunt down so-called rogue fighters who ignored the six-month order, which was issued in August. Al-Sadr's followers claim this is a pretext to crack down on their movement.

The maverick cleric announced earlier this month that he would not renew the order unless the Iraqi government purges "criminal gangs" operating within security forces he claims are targeting his followers.

That was a reference to rival Shiite militiamen from the Badr Brigade who have infiltrated security forces participating in the ongoing crackdown against breakaway militia cells the U.S. has said were linked to Iran.

The political commission of al-Sadr's movement and some lawmakers and senior officials said they were urging him to follow through with his threat, pointing to recent raids against the movement in the southern Shiite cities of Diwaniyah, Basra and Karbala.

"We presented a historic opportunity when we froze the (Mahdi) army," Nasser al-Rubaie, leader of the Sadrists in parliament, told reporters Monday. "But the step was negatively capitalized on."

The group planned to send the message to al-Sadr's main office in the holy city of Najaf, two Sadrist legislators and a member of the political commission told The Associated Press. They spoke on condition of anonymity because of fears of retribution.

"We have demanded that the government purge these security organs and release our detainees," one official said. "We have not found any positive response so far from the government, so why then should we continue freezing the (Mahdi Army)?"

Al-Sadr's political commission is made up of the movement's most powerful officials whose opinion often reflects that of the reclusive cleric, although the officials stressed that he retains sole decision-making authority over the militia.

Underscoring the complaints, the military announced the arrest Monday of a man accused of gathering intelligence, using computers and forging documents as an associate of militia leaders involved in attacks on U.S.-led forces.

U.S. troops also detained 18 Al Qaeda-linked militants in two days of operations ending Monday north of Baghdad.

Mahdi Army militiamen fought U.S. troops for much of 2004, and al-Sadr has tirelessly called for the withdrawal of U.S. forces from Iraq.