BAGHDAD -- Militants launched attacks on security forces and Shiite Muslim civilians across Iraq on Monday, killing nearly 100 people in a spree of shootings and bombings that rattled the country and worsened tensions among its political elite.

At least 92 Iraqis were killed and more than 300 were injured. The number of dead and wounded rose steadily in the evening as reports trickled in from Mosul in the north, Basra in the far south and points in between. News channels broadcast familiar images of weeping women cloaked in black abayas, mangled motor vehicles and pools of water mixed with blood.

It was the worst day of political violence in Iraq since Dec. 8, when insurgent bombings in the capital killed at least 127. No one claimed responsibility, but the choice of targets and the coordinated nature suggested an operation by al-Qaida in Iraq and sometimes-allied Sunni Arab insurgents groups.

The attacks came amid an increase in violence following inconclusive March 7 elections that stirred sectarian tensions and threatens the dramatic security improvements of the last 30 months. The Obama administration plans to pull all but 50,000 U.S. troops from Iraq by September even as it is accused by conservatives in Washington of not doing enough to stabilize the country.

Prime Minister Nouri al-Maliki's Shiite alliance narrowly lost the election to a Sunni-dominated slate led by one of his predecessors in the job, Ayad Allawi. Critics have accused al-Maliki of violating the spirit of the country's democratic experiment by initiating legal maneuvers to retain his post, and Allawi's allies quickly blamed al-Maliki's government and his political machinations for the surge in violence.

Al-Maliki and his allies have accused politicians within Allawi's bloc of inflaming sectarian passions with their rhetoric.

The violence Monday suggested that the Sunni insurgency retains potency despite the killing last month of two senior al-Qaida leaders. Iraqi security forces also arrested two suspected al-Qaida members and four associates during security operations throughout Iraq on Monday, the U.S. military said in a news release.

The deadliest of Monday's bombings targeted a textile factory in predominantly Shiite Hillah, 66 miles south of the capital, during a shift change. At least 32 workers and passersby were killed, and more than 136 people were injured in the blast.

The rare attacks in Basra, which also is mostly Shiite, struck a market for bicycles and motorcycles in the center of the city and at gas station in a residential area north of the city populated by supporters of Shiite cleric Muqtada al-Sadr. At least 21 people were killed and 66 wounded in the two attacks, possibly the worst violence in the impoverished provincial capital since 2007. Security forces in the city halted vehicle traffic and imposed a curfew on the town of Zubeir, a Sunni region and previous stronghold of the insurgency.

Al-Maliki's allies said the insurgents would fail to shake the political process.

"We obviously condemn these horrible crimes committed by al-Qaida and the remnants of the previous regime," said Sheik Ali Allaq, a leader of al-Maliki's Dawa Party.