The bomber drove his pickup truck packed with dates and concealed explosives toward downtown Howaider on Saturday evening, just as residents were gathering to break the daylong fast they observe during the Muslim holy month of Ramadan.

He detonated the cargo on a street lined with bustling markets and cafes, killing at least 25 people and wounding 35 in the mostly Shiite Muslim town north of Baghdad.

An hour later, in the emergency room of nearby Baqubah General Hospital, Hilmi Kadhum, 22, lay on a bed, his face and head badly burned. Overwhelmed physicians scurried about treating the wounded, and women wailed for family members lost.

"When the explosion happened, I didn't feel anything but I heard people screaming," Kadhum said. "Then I found myself here."

The bombing was the deadliest incident in a day of violence across Iraq that claimed at least 50 lives. Three U.S. soldiers were killed, the military said, two in southern Baghdad when a roadside bomb struck their patrol and another when a landmine exploded in Baiji, 125 miles north of the capital.

In the insurgent stronghold of Husaybah, in western Iraq along the Syrian border, U.S.-led forces killed 10 suspected insurgents in two simultaneous raids on houses in different neighborhoods, the U.S. military said in a statement. Firefights ensued at both locations, and airstrikes were called in to destroy the buildings.

Ammar Marsoomi, a physician at the nearby Qaem Hospital, confirmed that at least five fighters were killed in the incidents, four of them foreigners.

Also in Husaybah, an airstrike Friday targeted a house where a senior member of the insurgent organization al Qaeda in Iraq was meeting with other suspected insurgent leaders, the military said in a statement.

The military said "sources indicated" that Abu Mahmud, believed to be a Saudi who commanded several cells of foreign insurgent fighters, had convened the gathering to plan an attack on occupation and Iraqi forces in the coming days, the statement said.

Mahmoud Farhan, a tribal leader in the area, said the house had been deserted by its owners and taken over by al Qaeda in Iraq. "At least nine fighters were killed in the attack," Farhan said. "Most of them are still under the wreckage. People are trying to take them out."

Al Qaeda in Iraq, which is led by Abu Musab Zarqawi, a Jordanian, posted a statement on the walls of mosques in Rawa, about 175 miles west of Baghdad, acknowledging that some of its fighters had been killed.

"Your brothers said goodbye to some of the Al Qaeda lions due to a cowardice Crusader attack on their house," it said. "You shall see, not hear, our reaction."

The day of bloodshed came as two political coalitions expected to win strong support in National Assembly elections set for December introduced their members at news conferences. Under Iraq's election law, parties band together to form lists that compete against one another.

Iraqi election officials told the Reuters news agency that 21 coalitions consisting of about 230 parties had registered by the Friday deadline. Two large blocs of Sunni Arab parties will participate, after most Sunnis boycotted the country's last legislative elections held in January.

"We recognize that Iraq is multi-ethnic and multi-sectarian," said Ayad Allawi, the former interim prime minister and a secular Shiite. Allawi belongs to the Iraqi National List, which includes Vice President Ghazi Yawar, a Sunni Arab, and Communist Party leader Hamid Majid Mousa. Allawi said his slate would work to "ward off dangers of sectarianism, or ethnic strife that could engulf the country in an endless spate of conflict."

The United Iraqi Alliance, a coalition of 17 political organizations, held a news conference at the home of Abdul Aziz Hakim, leader of the Supreme Council for the Islamic Revolution in Iraq, one of several Shiite religious parties leading the slate.

"This alliance has a wide and important mass base among our people," Hakim said.

Shammari reported from Baqubah. Special correspondents Bassam Sebti and K.I. Ibrahim in Baghdad contributed to this report.

Attendants rush a wounded man into a hospital after a car bomb exploded in Howaider, just as people were gathering to break the Ramadan fast.