BAGHDAD, Iraq – Suicide bombers infiltrated a line of police recruits and a crowd of Shiite pilgrims yesterday as insurgents killed 125 civilians and five American soldiers, escalating attacks while political factions worked to forge a coalition government.

The stark surge in post-election violence produced familiar but heartrending images on a day that was the fourth deadliest since the fall of Saddam Hussein in 2003.

A woman and an infant girl in a bright red jumpsuit lay in a pool of blood, their faces covered by a sheet as men ferried the wounded in pushcarts in Karbala, 50 miles south of Baghdad. Ball bearings lay scattered on the bare earth next to Shiite Islam’s holiest shrine in Iraq.

After the devastating attack in a Sunni insurgent stronghold 70 miles west of the capital, Ramadi, police recruits got back in line to continue the screening process, Marine Captain Jeffrey S. Pool said.

Prime Minister al-Jaafari, a Shiite, denounced the violence as an attempt to derail the political process at a time when progress was being made toward a broad-based government that would include the Sunni Arabs and thus possibly weaken the insurgency.

With the two-day death toll from attacks reaching 183, Iraq’s main Shiite religious party, the Supreme Council for the Islamic Revolution, issued a veiled threat to Sunnis supporting the insurgency that its patience was wearing thin.

But in a chord struck by several politicians yesterday, the party also condemned policies it said were imposed by the American-led coalition that were hampering Iraqi security forces’ counterterrorism work. The Americans have increased their oversight of Shiite-dominated security forces following widespread charges of abuse, especially of Sunni Arab detainees.

“Not allowing these two ministries to do their job means exposing helpless Iraqis to ruthless terrorists,” SCIRI said. “They should know that the patience of our people will not last for a long time with these sectarian dirty crimes.”

The warning to Sunnis carried the possibility of using militias such as the former military wing of SCIRI, the Badr Brigade, to exact vengeance against Sunni supporters of insurgents.

The secretary-general of the Badr Brigade, Hadi al-A’meri, also blamed the attacks on the American-led coalition. “Why are they putting obstacles in the way of the work of the Interior Ministry?” he asked.

The American Embassy in Baghdad said it was appalled by the attacks. “This terror aims simply to kill innocent Iraqis and provoke further conflict between them,” the embassy said.

The main Sunni coalition that is negotiating with Shiites and Kurds over a coalition government after the December 15 election, the Iraqi Accordance Front, denounced the violence but blamed Iraq’s leaders for allowing it to happen.