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 .
A car bomb explodes in the Shiite city of Kut . Police officials say attackers in Baghdad left behind a black flag . The flag represents the Islamic State of Iraq , which has ties to al Qaeda .