Baghdad, Iraq (CNN) -- Insurgents apparently tied to al Qaeda attacked a checkpoint in western Baghdad and killed five police officers early Tuesday, officials said.
In the eastern city of Kut, meanwhile, at least 20 people were killed and 50 wounded when a bomb in a parked car exploded at a busy outdoor market, according to officials at the interior ministry. Health ministry officials, however, said three people died and 62 were wounded in the Kut bombing.
Two other car bombs were defused by Iraqi security forces about half an hour after the first explosion, interior officials said. Such attacks have been uncommon in Kut, the provincial capital of the predominantly Shiite province of Wasit.
The gunmen in Baghdad, who police officials said used pistols equipped with silencers, left behind a black flag, which is used to represent the Islamic State of Iraq. The umbrella group includes a number of Sunni extremist organizations and has ties to al Qaeda in Iraq.
The same flag was left behind by insurgents after they attacked several security checkpoints and killed at least 16 people in a neighborhood in northeastern Baghdad last week.
The Islamic State of Iraq also claimed responsibility for last week's suicide attack on a television station in Iraq that killed at least six people and wounded 20.
Police officials said another officer was wounded Tuesday after a bomb attached to his vehicle exploded in the Hurriya district in northwestern Baghdad. Two bystanders also were injured, police said.
Separately, three roadside bombs exploded in two neighborhoods in the Iraqi capital Tuesday, wounding six people. Also, two mortar rounds landed in the Mansour district in western Baghdad, damaging a building, and two more mortar rounds struck Baghdad's international zone Tuesday.
Overall, violence in Iraq has dropped drastically over the past two years compared with the height of the sectarian war in 2006 and 2007, but bloodshed continues.
The country is at a critical period as U.S. officials continue with plans to end America's combat mission and draw down troops to reach 50,000 by the end of August.
According to the security agreement between the United States and Iraq, all American forces are scheduled to leave the country by the end of next year.
CNN's Mohammed Tawfeeq contributed to this report.