BAGHDAD (AP) — Car bombs tore through shopping areas within minutes of each other in mainly Shiite neighborhoods of the Iraqi capital on Sunday, killing at least 37 people and wounding more than 100.

The attacks come amid rising sectarian discord in Iraq and appear aimed at shaking Iraqis’ confidence in the Shiite-led government. The explosions struck at the start of the local workweek and primarily targeted outdoor markets.

Violence in Iraq has fallen since the height of sectarian fighting in 2006 and 2007, but insurgents still frequently launch lethal attacks against security forces and civilians. It was the third time this month that attacks have claimed more than 20 lives in a single day.

The attacks began with the detonation of a parked car loaded with explosives in the sprawling Shiite district of Sadr City Sunday morning. Two more parked cars later exploded elsewhere in the neighborhood.

Nima Khadum, a government employee, said the blasts shattered the windows of his Sadr City house. He said the air was heavy with smoke, while burning cars littered the street and the bodies of the dead and wounded lay nearby.

“The scene was a bloody one that brought to my mind the painful memories of the violent past,” he said. “I don’t see the benefit of security checkpoints that only cause traffic jams and don’t do anything to secure Baghdad. The government, with its failing security forces, bears full responsibility for the bloodshed today.”

Simultaneous explosions also hit the southeastern Baghdad neighborhood of al-Amin, where the force of the blasts left behind little except the mangled chassis of two cars.

An open-air market in Husseiniya, just northeast of the capital, and the Kamaliya area in Baghdad’s eastern suburbs were also hit.

Another car bomb exploded near street vendors and a police car in the central commercial district of Karradah.

Police and hospital officials provided the death toll, and said more than 130 people were wounded. They spoke on condition of anonymity because they weren’t authorized to brief reporters.

Casualties could have been even higher. Authorities carried out controlled explosions of two other car bombs they discovered in Husseiniya and Habibiya, near Sadr City, according to police.

There was no immediate claim of responsibility for the attacks, but similar ones have been orchestrated by Sunni extremists, such as al-Qaida’s local affiliate. The group, known as the Islamic State of Iraq, favors large-scale, coordinated attacks. It considers Shiite Muslims to be heretics and accuses them of being too closely aligned with neighboring Shiite powerhouse Iran.

As sectarian strife mounts, protesters drawn overwhelmingly from Iraq’s Sunni community have been staging weekly demonstrations and sit-ins since late December to rally against the government, which is led by Shiite Prime Minister Nouri al-Maliki. The protesters have rejected calls for violence and distance themselves from extremist groups such as al-Qaida.

There are also concerns that Sunni insurgents could step up attacks ahead of provincial elections scheduled for April 20. The ballot would be the first country-wide vote since the U.S. troop withdrawal more than a year ago.

Al-Maliki and the U.S. Embassy condemned the attacks. So did the United Nations envoy to Iraq, Martin Kobler, who said “all Iraqi leaders have a responsibility to stand up against these atrocious crimes.”

Later in the day, gunmen opened fire on a military post near the western city of Fallujah, killing one civilian and wounding five people, including two soldiers, according to Fallujah police. The city and nearby Ramadi have been the heart of the Sunni protests.

The blasts came a day after a suicide bomber pretending to ask for help assassinated Brig. Gen. Ali Aouni, the head of the Iraq Defense Ministry’s intelligence academy, and three of his bodyguards in the northern city of Tal Afar.

Sunday’s attacks brought to more than 100 the number of people killed in violent attacks in Iraq since the start of the month. A total of 178 were killed in January attacks, according to an Associated Press count.

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Associated Press writers Sinan Salaheddin and Sameer N. Yacoub in Baghdad contributed to this report.