Iraqi Prime Minister Nuri al-Maliki said his country would file a lawsuit in Iraqi and U.S. courts against a U.S. private security firm over the killing of Iraqi civilians in Baghdad in 2007, his office said in a statement.

According to the statement obtained by Xinhua on Tuesday, Maliki rejected a U.S. judge's decision to drop charges against five of the U.S. Blackwater's security guards who were involved in killing unarmed civilians at a crowded intersection in western Baghdad two years ago.

"The Iraqi government will sue the company to Iraqi and United States courts, and we reject the ruling issued by the American court acquitting the company of the crime of killing a number of citizens," the statement quoted Maliki as saying.

Maliki made the remarks during his visit on Monday to the southern city of Najaf, some 160 km south of Baghdad, to talk with the spiritual Shiite leader Grand Ayatollah Ali al-Sistani.

In September 2007, American guards of Blackwater opened fire on dozens of civilian cars at the busy Nissor Square, killing 17 people and wounding others.

The incident angered Iraqis who see it as a symbol of foreigners' disregard for their lives, at a time the guards protecting U.S. embassy personnel were given immunity for prosecution in Iraqi courts after the invasion in 2003.

Earlier, the Iraqi parliament and some top officials also rejected the U.S. judge's decision to throw out charges against the U.S. guards and demanded an appeal to prosecute the defendants.