BAGHDAD, Iraq – A suicide bomber struck a funeral for a Shiite politician’s nephew yesterday, killing at least 32 mourners, wounding dozens, and splattering tombstones with blood – part of a surge of violence as Iraqi leaders try to form a coalition government.

Altogether, 53 people died in the day’s attacks, which included two car bombings in Baghdad and a militant ambush on a convoy of 60 oil tanker trucks heading from Iraq’s biggest refinery to the capital.

The funeral bombing in Muqdadiyah, 60 miles north of Baghdad, bore hallmarks of Islamic extremist groups such as Al Qaeda in Iraq. Politicians said the attack was an attempt to hinder a broad-based government, or force the dominant Shiite alliance into further compromises. Shiites were said to be close to a deal on a coalition with Sunni Arabs and Kurds nearly three weeks after parliamentary elections.

The bomber struck as more than 100 mourners chanted a ritual Islamic prayer, “There is no god but God.” They were at the cemetery to bury a 14-year-old boy a day after he was killed in a failed assassination attempt on his uncle, Ahmed al-Bakka, the director of the local hospital.

“We were walking in the funeral procession when a strange person joined the crowd,” Amer Khazim,37,said. “Suddenly, there was a strong sound and we were turned upside down. … I saw many legs and hands flying all over the place.”

Mr. al-Bakka, who was not at the funeral, is the head of the local branch of the Dawa party. Prime Minister al-Jaafari leads the party, which is a main partner in the country’s largest Shiite political coalition, the United Iraqi Alliance.

A senior Dawa official, Ali al-Adib, said such attacks were meant to exert pressure on the United Iraqi Alliance to accept a less than optimal compromise in the formation of the government.

The U.N. secretary-general, Kofi Annan, noted that the “horrendous crime” was the latest in a series of increasingly violent attacks after the December 15 elections, and called on Iraqis not to undermine the democratic process.

Final results from the elections should be released within two weeks, and are expected to show the United Iraqi Alliance with about 130 of parliament’s 275 seats. That figure is well short of the 184 needed to form a government.

A partner in the largest Sunni Arab political group denounced the attack.

“The Islamic Party condemns such ugly acts that are aimed at dividing the country,” Nassir al-Ani said. “The perpetrators want to cause divisions and hinder the political process in Iraq, but they will fail, and we will establish a national unity government.”

Shiites have been targeted by extremist Sunni Arab groups such as Al Qaeda in Iraq, led by Jordanian-born terrorist Abu Musab al-Zarqawi. His organization wants to force Iraq into a sectarian conflict to force American-led coalition forces to leave.

While Islamic extremist groups were suspected in the funeral attack, an Internet posting in the name of a nationalist group, the Islamic Army in Iraq, claimed responsibility for the ambush of the tanker convoy.

The claim was posted on an Internet site commonly used by militant groups and could not be independently verified.

The Islamic Army in Iraq is one of the most active terror groups in the country. It is believed to include former Baathists and loyalists to Saddam Hussein along with Sunni Salafist Islamic extremists and former Palestinian Arab terrorists who lived in Iraq under Saddam’s rule.

Nobody was injured in the attack on the drivers, which came three days after the reopening of the Beiji refinery, Iraq’s largest. The refinery north of the capital had been closed since December 18 because of attacks on drivers, leading to hours-long lines at gas stations in Baghdad.

Meanwhile, roadblocks went up across Baghdad as police searched for Interior Minister Bayan Jabr’s sister, who was kidnapped Tuesday. Gunmen killed one of her bodyguards and seriously wounded another in the abduction.

The pan-Arab Al-Jazeera network said a previously unknown group called the al-Tha’r Battalion, Arabic for revenge, claimed responsibility for the abduction. It demanded the release of all women detainees, a stop to all raids by the Interior Ministry, and decreased fuel prices.

In other violence:

* A car bomb exploded near an outdoor market in Baghdad’s southern Dora district, killing seven people, police said.

* Another car bomb in northern Baghdad killed three civilians and a policeman, Major Mosa Abdelkareem said.

* A roadside bomb targeting an American patrol in Kirkuk hit a civilian car instead, killing three passengers, police Colonel Polla Mohammed said.