( CNN ) -- Iraqi police have won back full control of a ministry building stormed by gunmen who took civil servants hostage , the Interior Ministry and security sources said Thursday . Six gunmen were killed in the police operation to retake the Ministry of Transport in northeast Baghdad . Police killed four militants , while two of the militants detonated suicide vests , the sources said . Two police officers were killed and seven injured in the attack . The hostages were freed unharmed . Police earlier said that the militants had overrun the Ministry of Human Rights building , adjacent to the Ministry of Transport . Roads were blocked around the Iraqi capital following the attack , and areas leading to Baghdad 's fortified Green Zone were closed . Separately , two car bombs exploded Thursday in different areas in the northeast part of the capital , killing four people and injuring 14 others . One hit a popular market area , a police source said . The United Nations said 2013 was the deadliest year in Iraq since 2008 , with almost 8,000 people killed in violence , most of them civilians . Fears of all-out sectarian war have increased since fighting broke out at the end of last year to the west of Baghdad in Anbar province , where al Qaeda-backed militants and Iraqi security forces have been battling for control of Falluja and Ramadi . More than 140,000 people have been made homeless since the new conflict erupted , according to Iraq 's Ministry of Displacement and Migration . The United Nations said last week it was scaling up its humanitarian response to help those displaced by the violence . CNN 's Mohammed Tawfeeq contributed to this report .
NEW : At least four people are killed and 14 injured in two car bomb attacks in Baghdad . Civil ##ians taken hostage by gunmen are freed unharmed , security sources say . Iraqi police retake a building from gunmen , two of whom are killed . The United Nations says 2013 was the deadliest year in Iraq since independence .