( CNN ) -- Acts of terror and sectarian violence killed 659 Iraqis and injured almost 1,400 in November , according to casualty figures released by the United Nations Assistance Mission for Iraq . Bombings account for many of the deaths , but U.N. officials warn that they 're seeing a surge in execution-style killings that `` have been carried out in a particularly horrendous and unspeakable manner , '' said Nickolay Mladenov , the special representative of the U.N. secretary-general for Iraq . Two groups of execution-style killings were discovered Wednesday when Iraqi security forces found 13 unidentified bodies -- each shot in the head . Eight of the bodies were found in the Arab Jabour district , a Sunni enclave in southern Baghdad . Five other bodies turned up in al-Shulaa , a Shiite area in the northwestern part of the capital . `` The Iraqi authorities should take immediate steps to find and hold accountable the perpetrators of these crimes and to implement effective measures to ensure the protection of all citizens , '' Mladenov said in a statement . So far this year , 7,157 civilians and 952 Iraqi security forces have died in sectarian violence , according to U.N. figures . Bombings in Baghdad . Convulsions of violence in Iraq leave more than 20 dead . CNN 's Mohammed Tawfeeq contributed to this report .
More than 2,000 Iraqis were killed and wounded in Iraq in 2007 , US estimates . Many were killed by bombs , but U.N. officials warned of growth in execution - style killings . Iraq urges Iraqi security forces to step up and protect civilians . So far this year , more than 8,000 Iraqis have been killed .