Mortar rounds struck an Iraqi army base west of Baghdad on Monday, killing four officers and two soldiers, security officials said.
A brigade commander was among the dead in the attack, which took place in the Abu Ghraib area, the sources said.
The deaths came two days after five senior officers, including a division commander, and 10 soldiers were killed during an operation against militants in the mainly Sunni western province of Anbar.
Violence in Iraq has reached a level not seen since 2008, when the country was just emerging from a brutal period of sectarian killings.
On Sunday, Prime Minister Nouri al-Maliki said that a Sunni Arab anti-government protest camp in Anbar had become a "headquarters for the leadership of Al-Qaeda," calling on legitimate protesters to leave before security forces move in.
Protests broke out late last year in Sunni-majority areas of Iraq, where people complain of being both marginalized by the Shia-led government and unjustly targeted by heavy-handed security measures.
Experts say that widespread Sunni anger has been a major factor in the heightened unrest this year.
Death tolls from violence surged after security forces raided an anti-government protest site near the northern town of Hawijah on April 23, sparking clashes in which dozens died.
More than 6,650 people have been killed in Iraq since the beginning of the year, according to AFP figures based on security and medical sources.