Two mortar bombs landed in Baghdad's heavily fortified Green Zone government and diplomatic area on Monday, wounding five people, Iraqi police said.
One loud blast woke many residents in the Iraqi capital at dawn.
Police said the mortar bombs damaged several cars in the Green Zone, which used to be under the control of the U.S. military but was handed over to Iraqi security forces last year.
Overall violence in Iraq has fallen sharply in the past two years but Sunni Islamist militant groups like al Qaeda still launch bomb attacks in an effort to undermine the Shi'ite-led government of Prime Minister Nuri al-Maliki.
Suicide bombings of government buildings and hotels in Baghdad in August, October, December and January killed hundreds of people, undermining confidence in Iraqi security forces ahead of March 7 parliamentary elections.
The elections are widely viewed as a milestone, with U.S. forces preparing to withdraw from Iraq by the end of 2011 and Baghdad signing deals with global oil firms that could soon produce billions of dollars in revenues.
Sunni militants regard Shi'ite Muslims as apostates and the rise to political power of Iraq's Shi'ite majority after the ousting of Saddam Hussein in the 2003 U.S.-led invasion generated a fierce Sunni-based insurgency.