Influential members of Muqtada al-Sadr's movement have urged the anti- U.S. Shiite cleric not to extend a cease-fire when it expires next month, officials said Monday, a move that could jeopardize recent security gains.

The Iraqi Red Crescent organization, meanwhile, gave a higher death toll than Iraqi officials from last week's devastating house explosion in the northern city of Mosul.

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.

Al-Sadr's August order for his feared Mahdi Army militia to freeze activities for six months was seen by U.S. commanders as a major factor in a nationwide reduction of violence.

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 this is a pretext to crack down on their movement.

The maverick cleric has threatened not to renew the cease-fire unless the government of Prime Minister Nouri al-Maliki 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.

His fighters were blamed for much of the retaliatory sectarian violence against Sunnis after the February 2006 bombing of a Shiite shrine in Samarra, and the cease-fire has been credited with a dramatic drop in the group's signature attacks—execution-style killings and kidnappings.

The U.S. military has said an influx of some 30,000 additional American troops working more closely with Iraqi security forces and a Sunni revolt against Al Qaeda in Iraq are other major factors in the lull in violence.

But while major inroads have been made, Iraqis continue to face attacks, even in the capital, which is at the center of the security crackdown.

A roadside bomb struck a minibus carrying a coffin and mourners to a funeral in the predominantly Shiite southeastern neighborhood of New Baghdad, killing three passengers, a police officer said.

The bomb apparently was meant for a police patrol but missed its target and blew up near the bus instead, a police officer said.