( AP ) - A suicide car bomber killed at least 13 Iraqi soldiers and wounded dozens more people in Iraq's north on Sunday. Meanwhile, the U.S.-protected Green Zone in Baghdad came under fire from either mortars or rockets, and a round that fell short injured two bystanders.
The Easter Sunday attacks underscored the fragility of Iraq's security, despite a decline in violence over the past year. They also came as the U.S. military death toll in Iraq nears 4,000.
Iraqi security forces opened fire on the bomber as he drove toward the military base in the northwestern city of Mosul but were unable to foil the attack because the truck's windshield had been made bullet-proof.
The attacker blasted through an armored vehicle to reach the courtyard of the military headquarters, according to an Iraqi army officer, who spoke on condition of anonymity because he wasn't authorized to release the information.
Police said at least 13 Iraqi soldiers were killed and 42 people wounded - 30 soldiers and 12 civilians - in the attack. Mosul, 225 miles northwest of Baghdad, has been described by the U.S. as the last urban stronghold of the Sunni-led al-Qaida in Iraq.
Shiite extremists were suspected to be behind the barrages against the Green Zone, which houses the U.S. and British embassies and the Iraqi government headquarters.
About 10 detonations were heard starting shortly before 6 a.m in the sprawling area in central Baghdad. Several other mortars or rockets slammed into the area about four hours later.
The U.S. public address system in the Green Zone warned people to "duck and cover" and to stay away from windows following both attacks.
No casualties were reported inside the Green Zone, a frequent target of rocket and mortar attacks that is located on the west bank of the Tigris River. But one round fell short and exploded in a major traffic circle on the east side of the river, injuring two people nearby, police said.
There were no claims of responsibility for the barrages, but it appeared the rounds were fired from areas of eastern Baghdad where the biggest Shiite militia, the Mahdi Army of radical cleric Muqtada al-Sadr, operates.
A cease-fire called by al-Sadr, along with an increase in U.S. troop levels and a move by American-backed Sunni fighters to turn against their former al-Qaida in Iraq allies, have been credited with sharply reducing violence in Baghdad and surrounding areas.
But there are fears that the cease-fire may unravel after a series of clashes between U.S.-Iraqi forces and Shiite militiamen in Baghdad, Kut and other areas south of the capital.
Last month, the U.S. military blamed what it calls Iranian-backed Shiite militias for a series of deadly rocket attacks in Baghdad. Those included one that struck Camp Victory, the main U.S. military headquarters, and an Iraqi housing complex on the capital's southwestern outskirts on Feb. 18, killing at least five people and wounding 16, including two U.S. soldiers.
The military said the extremists were among factions that have broken with al-Sadr and refused to follow his cease-fire order. Iran denies allegations that it is stoking the violence. Al-Sadr recently extended the cease-fire through mid-August.
In other violence Sunday, a blast killed eight, including two women and two children, in southeastern Baghdad, police said. The cause of the explosion was not immediately known.
On Saturday, U.S. officials said three American soldiers were killed in a roadside bombing that also killed two Iraqi civilians northwest of Baghdad. The latest deaths brought to 3,996 the number of U.S. service members and Pentagon civilians who have died since the war began on March 20, 2003, according to an Associated Press count.
A suicide bomber late Saturday also drove a truck laden with explosives into the home of the mayor in Samarra, 60 miles north of Baghdad. Three security guards were killed and four others injured, police said.