Joao Silva for The New York Times

Residents gathered around destroyed vehicles in the Shuala neighborhood of Baghdad after a car bombing.

At Least 51 Die in Attacks Across Iraq

BAGHDAD — The shelling started just before 6 a.m., mortar fire shaking buildings and sending early risers in the Green Zone here running for shelter. Sirens went off, and loudspeakers blared, "Duck and cover! Duck and cover!" A thick column of gray smoke rose above the embassies and government buildings in the area.

The early morning onslaught on Sunday was one of the fiercest and most sustained attacks on the Green Zone in the past year, and it ushered in a day of violence that claimed the lives of at least 51 Iraqi civilians and soldiers, including two children.

Philip T. Reeker, a spokesman for the American Embassy, said the mortar attacks had caused "no deaths or major injuries" within the Green Zone. He noted that for security reasons, American officials do not release details of such attacks. But one mortar shell fell short of the zone and landed in the Bab al-Sharji neighborhood in central Baghdad, killing one person and wounding five others, according to Iraq's Interior Ministry. Another fell in the Karrada near the house of Vice President Adel Abdul Mahdi, but no casualties were reported, the Iraqi police said.

Witnesses said that the mortar shells — from 6 to 10, according to different accounts — were fired from Baladyat, a Shiite neighborhood in eastern Baghdad.

Several more volleys of mortar fire aimed toward the Green Zone followed during the day, including a series of intense blasts just before 8:30 p.m.

One mortar round landed on the west bank of the Tigris, just outside the Green Zone wall, igniting a large brush fire.

American military officials have in the past blamed such attacks on Shiite militia factions or "special groups" that have received backing from Iran. The factions are thought to be splinter groups within the Mahdi Army militia founded by the Shiite cleric Moktada al-Sadr.

Last month, Mr. Sadr announced the extension of a cease-fire begun last year and said that he would not tolerate any violations of the order.

In the Shuala area of western Baghdad on Sunday, a bomb in a parked car exploded, killing six and wounding at least 10. The explosion tore through the neighborhood's main street of houses and shops.

"We were having our lunch inside the restaurant when we heard a big sound of explosion which broke the front glass of shop," said Abbas Qasim, 38, the owner of a store on the street.

" I almost suffocated while I was eating and when I got out, I saw four cars burning," he said. "One of them was a van carrying students who just got back from the university. I rushed to help them with some locals but five of them were already dead and riddled with shrapnel."

Ali Mahmoud, 45, said that the explosion was the first in the neighborhood in two years.

"The American war planes were shelling most of the area all last night because of the Madhi Army," he said. "This car bomb is a message for us because our neighborhood is dominated by the Mahdi Army."

Violence also struck the Zafaraniya neighborhood, in the southern part of the capital, where gunmen in three cars opened fire on pedestrians, killing seven and wounding 16.

In the north of Iraq, a suicide bomber in a truck smashed through a barrier of armored vehicles in front of an Iraqi Army garrison in the al-Haramat neighborhood of Mosul. The bomb, when it detonated, killed 12 soldiers and wounded 42 other soldiers and civilians.

The wounded, American military officials said, "were evacuated to local medical facilities for treatment or treated on-site."

American forces also reported killing "12 terrorists," after they attacked ground troops east of Baquba.

In a statement, the military said that American troops had ordered the occupants of a building to come outside.

"Some complied but others remained inside," the statement said. "Coalition forces entered the building and were fired upon by several armed men."

The statement said that six of the men who were killed had shaved the hair off their bodies, which, the military said, was consistent "with final preparation for suicide operations."

But an official of the Baquba police said that American war planes had shelled the house, which belonged to Khudhaier Salem, a prominent senior figure in the region, killing 13 and wounding nine, including people in neighboring houses.

Also in Baquba, two children were killed when they picked up an improvised explosive device, police officials said.