At least nine people were killed and 17 others wounded on Monday when insurgents detonated an oil tanker packed with explosives inside a governmental compound in the Iraqi city of Tikrit, police said.
No group immediately claimed responsibility for the attack, but Sunni Muslim insurgents tied to al Qaeda have been redoubling their efforts to undermine Iraq's Shi'ite-led government and foment inter-communal conflict this year.
The blast exploded in central Tikrit, 150 km (95 miles) north of Baghdad, 15 minutes after insurgents drove the tanker inside a compound housing governmental administrative offices. It killed nine people including seven policemen.
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.
"The tank was stopped just behind the police administration building and partially damaged it. I was injured in my face and stomach because of glass," Captain Mohammed Salih said.
Intensifying violence has accompanied by political crisis in Iraq where a power-sharing government among Shi'ite, Sunni and ethnic Kurdish blocks has been all but paralyzed since U.S. troops left more than a year ago.
Prime Minister Nuri al-Maliki, a Shi'ite, is also facing months of protests in the Sunni heartland, which shares a border with Syria. Many Iraqi Sunnis feel their minority sect has been sidelined by Maliki's government.
Security experts say al Qaeda-linked militants have been regrouping in the western province of Anbar and crossing into Syria to fight alongside mainly Sunni rebels against forces loyal to President Bashar al-Assad, an ally of Shi'ite Iran.