BAGHDAD, Iraq (AP) – Twin bombings Monday tore through stalls of vendors selling second-hand clothes and DVDs in a busy Baghdad market catering to Shiite Muslims during a religious festival. A market also was attacked north of the capital, and police said nearly 100 people died in the renewed campaign blamed on Sunni Muslim insurgents.

The U.S. military also reported the deaths Sunday of two Marines, raising the two-day death toll to 27 in a particularly bloody weekend for American forces in Iraq. A roadside bomb killed a U.S. soldier and wounded four others Monday in northern Iraq, it said.

Monday’s first blast, a parked car bomb, hit shortly after noon in the Bab al-Sharqi market between Tayaran and Tahrir squares one of the busiest parts of Baghdad. Seconds later, a suicide car bomber drove into the crowd.

Police estimated that each car was loaded with nearly 220 pounds of explosives.

Deputy Health Minister Hakim al-Zamili said at least 78 people were killed and 156 were wounded, making it the deadliest attack in two months. Figures provided by police and hospital officials showed that as many as 88 people were killed.

The explosions left body parts strewn on the bloodstained pavement as black smoke rose into the sky. Police sealed off the area as ambulances rushed to the scene.

Survivors were taken to nearby al-Kindi Hospital where emergency personnel worked feverishly over the bloodied and badly wounded.

Bodies covered in blue and white cloth littered the outdoor courtyard at the hospital. Family members and friends were at the side of the dead, screaming in grief and crying out oaths.

A suicide bomber killed at least 63 people in the same area last month.

Prime Minister Nouri al-Maliki, a Shiite, denounced the attack.

“We condemn this crime and we promise that the security forces will pursue all those involved in this crime and bring them to justice,” he said in a statement.

Hours later, a bomb followed by a mortar attack struck a market in the predominantly Shiite town of Khalis, 50 miles north of Baghdad, killing at least 12 people and wounding 29, police said.

The twin bombing in Baghdad was the single deadliest attack against civilians in Iraq since Nov. 23, when suspected al-Qaida in Iraq fighters attacked Baghdad’s Sadr City Shiite slum with a series of car bombs and mortars that struck in quick succession, killing at least 215 people.

In other violence, gunmen killed a teacher as she was on her way to work at a girls’ school in the mainly Sunni area of Khadra in western Baghdad, police said, adding that the teacher’s driver was wounded in the drive-by shooting.

Two mortar shells also landed on a primary school in the Sunni stronghold neighborhood of Dora in southern Baghdad, killing a woman waiting for her child and wounding eight students, police said.

Police also said that a cell phone company employee and a Sunni tribal chieftain were killed in separate shootings in Baghdad, while the bullet-riddled bodies of three men were found elsewhere in the capital. An oil technician also was shot to death in the northern city of Mosul, police said.

The two U.S. Marines were killed Sunday in separate attacks in the Anbar province, an insurgent stronghold west of Baghdad, the military said. The deaths came a day after 25 U.S. troops were killed Saturday in the third-deadliest day since the war started in March 2003 _ eclipsed only by the one-day toll of 37 U.S. fatalities on Jan. 26, 2005, and 28 on the third day of the U.S. invasion.

The heaviest tolls Saturday came from a Black Hawk helicopter crash in which 12 U.S. soldiers were killed northeast of Baghdad as well as an attack on a provincial government building in the Shiite holy city of Karbala that left five U.S. troops dead.

Col. David Sutherland, the commander of U.S. forces in the strife-ridden Iraqi province of Diyala, said the U.S. military has not ruled out hostile fire.

The violence underscores the challenges faced by U.S. and Iraqi forces as they seek to rein in Sunni insurgents and Shiite militias that have made the capital and surrounding areas a battleground.

Meanwhile, two government officials said Sunday that al-Maliki dropped his protection of an anti-American cleric’s militia after being convinced by U.S. intelligence that the group was infiltrated by death squads.

Al-Maliki’s turnaround on the Mahdi Army was puzzling because as late as Oct. 31, he had intervened to end a U.S. blockade of Sadr City, the northeast Shiite enclave in Baghdad that is headquarters to the militia.

Shiite militias began taking revenge after more than two years of incessant bomb and shooting attacks by Sunni insurgents.

Sometime between late October and Nov. 30, when the prime minister met President Bush, al-Maliki was convinced of the truth of American intelligence reports that contended, among other things, that his protection of radical cleric Muqtada al-Sadr’s militia was isolating him in the Arab world and among moderates at home, two government officials said.

“Al-Maliki realized he couldn’t keep defending the Mahdi Army because of the information and evidence that the armed group was taking part in the killings, displacing people and violating the state’s sovereignty,” said one official.

Both he and a second government official who confirmed the account refused to be identified by name because the information was confidential. Both officials are intimately aware of the prime minister’s thinking.

“The Americans don’t act on rumors but on accurate intelligence,” said the second official, confirming the Americans gave al-Maliki overwhelming evidence about the Mahdi Army’s deep involvement in the sectarian slaughter.

On Friday, in a bid to fend off an all-out American military offensive, al-Sadr ordered 30 lawmakers and six Cabinet ministers under his control to end their nearly two-month boycott of the government. They were back at their jobs Sunday.

Al-Sadr had already ordered his militia fighters not to display their weapons. They have not, however, ceded control of the formerly mixed neighborhoods they have captured, killing Sunnis or forcing them to abandon their homes and businesses.

The first government official said al-Maliki’s message to al-Sadr was blunt:

“He told the sheik that the activities of both the Sadrist politicians and the militia have inflamed hatred among neighboring Sunni Arab states that have been complaining bitterly to the Americans.”