A car bomb blasted through a busy bus station near one of Iraq's holiest shrines Saturday, killing at least 56 people, police and hospital officials said. Separately, a suicide car bomb killed 11 people on a major bridge in downtown Baghdad - the second attack on a span over the Tigris river this week, police said. The Jadriyah bridge suffered little damage. The bus station bombing occurred about 200 meters from the Imam Hussein shrine in Karbala, where the grandson of Islam's Prophet Muhammad is buried - one of the most important sites for Shiites. State television aired footage from the scene, in which rescue workers could be seen evacuating casualties. The charred body of a child laid motionless on a stretcher. At least six children were among the dead, according to an official at Al-Hussein Hospital. Iranian and Pakistani pilgrims were also among the casualties, he said on condition of anonymity because he was not authorized to release the information. Hundreds of people swarmed around ambulances, crying out and pounding their chests. Police fired into the air to disperse crowds and clear roads for emergency vehicles, but angry mobs attacked them and set two police vehicles on fire. Rioters surrounded the Karbala governor's office and demanded his and provincial council members' resignations - blaming them for lax security. Mobs threw stones at the governor's office and set fire to the building. A curfew was imposed in the area, and the city's entrances were sealed off while police and soldiers patrolled the streets. More than 70 people were also wounded in the attack, said another official at Al-Hussein Hospital. Karbala lies 80 kilometers south of Baghdad, and is the destination of an annual Shi'ite pilgrimage. Hundreds of Shiite faithful were killed traveling back and forth to the city during this year's pilgrimage, which took place last month. In Baghdad, at least 15 people were wounded in the Jadriyah bridge bombing - the second such attack this week on infrastructure connecting the Iraqi capital's two sides. On Thursday, a suicide truck bomb completely collapsed the al-Sarafiyah bridge in northern Baghdad, killing 11 people and sending cars plummeting into the waters below. Police said four would-be suicide attackers were killed Saturday in the northern city of Kirkuk when one of them detonated his explosives belt prematurely. All four men were killed but no civilians were hurt, said police Brig. Adil Zain-Alabideen. He said all four were insurgents embarking on an attack mission, but did not elaborate. Kirkuk lies about 290 kilometers north of Baghdad. Also Saturday, gunmen attacked the western Baghdad house of Adnan al-Dulaimi, head of the largest Sunni bloc in Iraq's parliament, police said. Al-Dulaimi was not at home at the time of the attack, and is believed to be in Jordan. Clashes erupted between his guards and the gunmen, lasting about half an hour. Five guards were wounded, police said. Al-Dulaimi's group, the Iraqi Accordance Front, has 44 seats in parliament. In other violence, a policeman was killed Saturday in a drive-by shooting in Hillah, about 95 kilometers south of Baghdad, police said. A bomb planted in a garbage can missed a passing police patrol in Baghdad's southwestern Baya district Saturday, but injured three electricity workers who were working nearby, police said. The US military issued a statement saying American troops captured 17 suspected insurgents, including an alleged al-Qaida in Iraq member, during raids Saturday morning.