Around 60 people have been killed and up to 150 wounded in a suicide bombing at a police recruitment centre in the Kurdish city of Irbil in northern Iraq.
The bomber blew himself up among police recruits
The bomber posed as a volunteer to get into the compound and mingled with young men seeking jobs before setting off explosives, Kurdish officials said.
It was the bloodiest single attack in the region since the war, and follows an escalation in violence across Iraq.
It came less than 24 hours after a new but incomplete government was sworn in.
Later in the day, a car bomb in Baghdad was reported to have killed nine Iraqi National Guardsmen and wounded at least 16 other people.
Members of Iraq's police force and police volunteers are frequently targeted by insurgents, who view them as collaborators with US-led forces.
Last year, at least 101 people were killed in twin suicide bombings in Irbil, about 350km (217 miles) north of Baghdad.
A message on an Islamist website purportedly from the militant group Ansar al-Sunna, which is believed to have links to al-Qaeda, said that the group had carried out the Irbil attack.
The blast happened at a local office of the Kurdistan Democratic Party (KDP) which also housed an interior ministry compound for northern Iraq's regional government.
Farid Makhdid, a 28-year-old policeman, told Reuters news agency: "I was standing outside. All I remember is seeing a huge explosion and seeing many people that were injured and killed."
MAJOR ATTACKS SINCE JAN POLL
4 May: At least 50 people killed in suicide attack on police recruits in Irbil
29 April: At least 29 people killed in wave of car bomb attacks on Iraqi security forces
10 March: 47 people killed by suicide bomber at Shia funeral in Mosul
28 February: Massive car bomb kills 125 people in Hilla
19 February: Suicide bombers kill 30 people during Shia Ashura celebrations
18 February: Around 29 people die in attacks in Baghdad and Iskandariya
7 February: Attacks on security forces kill at least 25 people in Mosul and Baquba
Television pictures showed pools of blood on the street as police tried to keep bystanders at bay.
There were scenes of chaos as ambulances and taxis ferried victims to local hospitals.
One witness said piles of bodies were taken away in pick-up trucks.
"A suicide bomber entered the recruiting centre and blew himself up," Irbil governor Nawzad Hadi told AFP news agency.
But he vowed: "We will continue fighting terrorists until we root them out. They will not scare us."
The attack in Irbil, a stronghold of KDP chief Massoud Barzani, came three days after 25 people were killed when a suicide bomber attacked a KDP official's funeral in the northern town of Talafar.
The latest blast comes as negotiations continue to fill several vacant posts set aside for Sunni Arabs in the new Iraqi cabinet.
The BBC's Jim Muir in Baghdad says Prime Minister Ibrahim Jaafari - a Shia Muslim - must bring credible Sunnis into his government to undercut the insurgency.
The Sunni Muslim minority, which largely boycotted Iraq's historic elections in January, lost power after the fall of Saddam Hussein.
A Kurdish bloc led by the Kurdistan Democratic Party (KDP) and its rival Patriotic Union of Kurdistan (PUK) came second in the elections. PUK leader Jalal Talabani was appointed Iraqi president last month.