A suicide car bomber blasted a police station the northern oil city of Beiji. Four policemen were killed and eight injured.
The attack came a day after the bombing of a key oil pipeline just east of the northern oil city of Beiji .
Saturday's explosion occurred at 9:30 a.m. at a police station about five kilometers (three miles) north of the city center, police said.
Beiji - which lies 250 kilometers (155 miles) north of Baghdad - houses northern Iraq's largest oil refinery, and serves as a key transfer point for crude oil being exported out of Iraq. Attacks on the Kirkuk-Beiji pipeline cluster have been infrequent in recent months, with some 300 U.S. soldiers and more than 2,000 Iraqi troops guarding the zone.
The Russian delegation to the UN denied reports about Russian nuclear forces on high alert