BAGHDAD, Iraq — A suicide bomb attack on a Baghdad market killed at least 88 people yesterday and another 12 were killed in a separate suicide bomb attack in one of the bloodiest days since the American invasion of Iraq in 2003.

The attack on the Bab al-Sharji market in northern Baghdad came as American and British forces prepare a major operation to crush the insurgency in the lawless city.

A bomb in a parked car tore through stalls selling CDs and second-hand clothes shortly after noon. Seconds later, a suicide car bomber drove into the crowd.

The market is a stronghold of the Madhi army, the main Shiite militia in central Iraq.

Interior Ministry sources said each car was packed with 165 pounds of high explosives. Shops and market stalls were destroyed, creating deadly flying debris.

The bombers appeared to target an area that sold CDs of Shiite songs, a witness, Ali al-Saiedy, said: “All of the people who were working there are Shia with the Mahdi army. We believe that we been attacked by Sunnis.”

Prime Minister al-Maliki condemned the attack and blamed groups that refused to accept a democratic state.

“Those terrorists who committed this crime think in their bloody attitude that killing a large number of citizens will lead to breaking the Iraqi people’s will and tearing apart its unity,” he said.

Survivors were treated at al-Kindi Hospital. Bodies covered in blue and white cloth littered its outdoor courtyard.

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.

The market bombing in Baghdad was the single most deadly attack against civilians in Iraq since November 23, when at least 215 people were killed in Sadr City, a Shiite slum, by a series of car bombs and mortars.

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

While Shiite militias increasingly dominate Baghdad’s neighborhoods, the heavily Sunni outskirts are becoming staging grounds for attack.

President Bush’s surge of American troops is designed to increase residential security, but commanders around the city are not gaining additional troops to intercept explosives and weapons caches.

Colonel Michael Kershaw, commander of the 10th Mountain Division, which has the job of tackling Sunni groups in a former no-go area southwest of Baghdad known as the “triangle of death,” told his troops yesterday: “We can’t stop all extremists from launching attacks into Baghdad. Some will get through. What we can do is cut down their freedom of maneuver until it’s too dangerous for them to operate.”

Working alongside the Iraqi army, Colonel Kershaw hopes to disrupt terrorist “rat lines” that previously allowed easy passage into Baghdad.