A bombing Monday outside a restaurant in Baghdad that is popular with police left at least seven dead and more than 80 wounded.
"All these people were killed for no reason,” one officer said.
The strike followed the assassination of a top national security official who was killed along with his driver when two carloads of gunmen opened fire on their car in the capital.
Al-Qqeda in Iraq has claimed responsibility for that attack.
Other violence in Iraq today has left seven people dead and the U.S. military says five U.S. soldiers died Sunday in northern Iraq.
Meanwhile, almost 300 suspected insurgents have been detained in a joint U.S.-Iraqi military offensive in Baghdad.
A U.S. military spokesman says “Operation Squeeze Play” is the largest combined operation with Iraqi security forces to date.
The offensive is targeting militants suspected of attacking the U.S. detention facility at Abu Ghraib and along the road linking Baghdad to the international airport.
The military also says it confiscated weapons and $6 million in U.S. currency during a separate sweep in Baghdad.
No specific troop numbers were provided but at least 2,000 soldiers are believed to be taking part.