A fuel lorry has exploded after speeding towards a Baghdad police post, killing at least nine and injuring more than 50 other people, officials say.
Iraqi police have been frequently targeted by insurgents
Witnesses described seeing a vehicle being driven into the car park shortly after 0800 local time (0400 GMT) as people were arriving for work.
Ambulances and firefighters raced to the scene in the Seidiyeh district.
Separately, the Iraqi defence ministry reported that one of its senior officials has been killed in Baghdad.
Issam Jassem Qassim, a
director general in the ministry, is said to have been shot dead on Sunday night by several gunmen near his home in a southern district of the city.
Monday morning's blast was the latest in a string of bombings that have targeted Iraqi police and government officials.
Witnesses said a fuel tanker suddenly appeared as the police were gathering to start their shift.
"We were all standing in a row, listening to our officer as he gave us our assignment for the day," Mehdi Salah Abed Ali, 32, told the Associated Press news agency from his hospital bed.
"There were many policemen standing in the square when the tanker exploded," he said.
ATTACKS SINCE HANDOVER
19 July - Attack on Baghdad police station, nine killed
17 July - Car bomb in Baghdad targets Iraqi justice minister, killing four of his guards
15 July - Car bomb targets police station in Haditha, west of Baghdad, killing 10
14 July - Governor of Mosul killed in ambush
14 July - Car bomb explodes near seat of government in Baghdad, killing 10 and wounding 40
Television pictures from the scene showed a huge crater in the street, with debris scattered over a large area.
The blast ripped through a roof covering police vehicles but the station itself sustained only minor damage.
US Colonel Bill Salter told Reuters news agency that the attack was probably carried out by a suicide bomber.
"We believe it was possibly a fuel-type truck vehicle," he told reporters.
Health ministry officials said about 56 wounded people had been taken to Baghdad's Yarmuk hospital.
In a separate attack minutes after the explosion, insurgents fired a rocket-propelled grenade at a fire station near the heavily fortified US military compound in Baghdad.
"It was an RPG attack on the al-Salihiya fire station. One person was wounded," a US spokesman told AFP news agency.
Iraqi Prime Minister Iyad Allawi has vowed to crush the insurgents behind the attacks, announcing plans for a new intelligence unit to "annihilate those terrorist groups".
He is in Jordan as part of a Middle East tour to try to improve ties with Iraq's neighbours and to discuss security issues.
Tough new laws have been introduced, allowing the government to impose martial law in certain areas, declare curfews, set up checkpoints and detain suspects.
But the BBC's Peter Greste in Baghdad says intelligence sources report that over the past 48 hours there have been 66 separate incidents across the capital, ranging from roadside bombs to shootings.
The emotional as well as physical toll continues to grow
This all suggests, our correspondent says, that far from fading away, the insurgency is growing increasingly organised and active.
Iraqi police have borne the brunt of many of the attacks.
"They say we collaborate with the coalition. We don't collaborate; we just protect our nation. We protect the land of Iraqis," police officer Amer Shaker Mehdi told Reuters.