Insurgent attacks killed six Iraqi policemen and two civilians in a fresh surge of violence.
A lull in attacks followed the Dec. 15 parliamentary elections. But that ended on Sunday, when 18 people were killed. On Monday, shootings and bombings killed at least two dozen people, including a U.S. soldier.
Officials said insurgents were trying to deepen the political turmoil surrounding the contested vote. Preliminary figures have given a big lead to the religious Shiite bloc that controls the current interim government.
The new violence came as three opposition groups threatened a wave of protests and civil disobedience if fraud charges are not properly investigated. The warning came from the secular Iraqi National List, headed by former Shiite Prime Minister Ayad Allawi, and two Sunni Arab groups.
More than 10,000 people, some carrying photos of Allawi, demonstrated Tuesday in favor of a government that would give more power to Sunni Arabs and secular Shiites. Marches chanted "No Sunnis, no Shiites, yes for national unity."
"We're protesting to reject the elections fraud. We want to ask the government and the elections commission: 'Where did our votes go? Who stole them?"' said Abdul Hamid Abdul Razza, a 45-year-old barber.
On Tuesday, clashes erupted between gunmen and Iraqi police in Baghdad, killing two policemen and two bystanders, Capt. Firas Keti said. South of Baghdad, a roadside bomb targeting a police patrol killed two officers, and gunmen in southern Baghdad killed another, police said.
Gunmen southeast of Kirkuk, 180 miles north of Baghdad, killed one police officer and wounded two, Capt. Farhad Talabani said.
The U.S. military on Tuesday said two U.S. pilots died in a helicopter accident in western Baghdad. The accident was under investigation; the military said no hostile fire was involved.
Iraq's Electoral Commission said Monday that final results for the 275-seat parliament could be released in about a week.
Sunni Arab and secular Shiite factions are demanding that an international body review more than 1,500 complaints, warning they may boycott the new legislature. They also want new elections in some provinces, including Baghdad. The United Nations has rejected an outside review.
"We will resort to peaceful options, including protests, civil disobedience and a boycott of the political process until our demands are met," said Hassan Zaidan al-Lahaibi of the Sunni-dominated Iraqi Front for National Dialogue. He spoke in neighboring Jordan, where representatives of the groups have met in recent days.
The election commission considers 35 of the complaints serious enough to change some local results. But Farid Ayar, a commission official, said there was no reason to cancel the entire election.
He also said preliminary results from early votes by soldiers, hospital patients, prisoners and overseas Iraqis showed a coalition of Kurdish parties and the main Shiite religious bloc each taking about a third. Those nearly 500,000 votes were not expected to alter overall results significantly.
Preliminary results previously released gave the United Iraqi Alliance, the religious Shiite coalition dominating the current government, a big lead — but one unlikely to allow it to govern without forming a coalition with other groups.
Bahaa al-Araji, a member of the Shiite alliance, said the group was preparing to negotiate with other political blocs and had already met with the Sunni Arab Iraqi Islamic Party.
Al-Araji also said likely candidates for prime minister were current Prime Minister Ibrahim al-Jaafari, who heads the Islamic Dawa party, and Adel Abdul-Mahdi, who belongs to the other main Shiite party, the Supreme Council of the Islamic Revolution in Iraq.