A suicide bomber blew up a tanker truck at police headquarters in the Iraqi city of Tikrit, killing nine people and wounding 11 people, police and medics said.
Most of the casualties in the attack on Monday morning were police officers.
The bomber drove the tanker inside a compound housing governmental administration offices in central Tikrit, 150km north of Baghdad, setting off a blast that left behind a large crater and badly damaged nearby buildings.
Initial accounts reported the truck had been abandoned at the site. Police at the scene said compound guards may not have suspected the tanker because fuel trucks arrive every morning to deliver gas and oil to the government offices.
Over the past years, Tikrit, which was the hometown of executed dictator Saddam Hussein, remains a focus for insurgents and a hotbed of sectarian violence.
No one claimed responsibility for the attack, but Sunni Muslim insurgents have stepped up their efforts to undermine Iraq's Shia-led government and foment inter-communal conflict this year.
Also north of the capital in the town of Tuz Khurmatu, gunmen wounded the mayor and his two bodyguards, officials said.
A day earlier a bomb exploded inside a mosque in Iraq's predominantly Shia Muslim south on Sunday, wounding six civilians, police said, as the country's delicate sectarian balance comes under growing strain.
The bomb exploded in the town of Zubair, around 25 km south of the usually stable oil hub of Basra.
Stepping up attacks
Ten years after the US invasion that toppled Saddam Hussein, Iraq is still grappling with political turmoil and Sunni fighters linked to al-Qaeda, who are stepping up attacks on Shia targets and security forces.
The recent attacks come in the run-up to provincial elections scheduled for April 20, due to be held in 12 of Iraq's 18 provinces, the country's first polls since a parliamentary vote in March 2010.
But questions have been raised over the credibility of the polls as they have been postponed in two provinces hit by months of protests, and 11 candidates have been killed, according to an AFP news agency tally.
Although markedly lower than its peak in 2006 and 2007, levels of violence remain high in Iraq - at least 267 people have been killed in attacks this month, the highest figure since August 2012.