The attack, which took place in Taji, began with a car bomb followed by a roadside bomb.

Among the casualties are police officers, the official said. Authorities fear the numbers will rise.

While violence has dramatically dropped since the height of sectarian violence a few years ago that nearly tore the country apart, attacks and bombings remain a daily occurrence.

The recent increase in attacks pushed June's death toll to the highest this year for Iraqi security forces and civilians. More than 270 people, including 155 civilians, were killed in attacks, Iraqi authorities said.

Fourteen US soldiers were also killed in combat-related incidents in June, the largest loss of life among US troops in Iraq since 2008.

The roughly 47,000 American troops in Iraq are due to withdraw by January 1, 2012, under a US-Iraqi security pact, though Iraqi Prime Minister Nuri al-Maliki is consulting with lawmakers over whether to request troops stay beyond the deadline.