The BBC said on Tuesday that government figures showed the monthly death toll in the Iraqi capital had jumped from about 1,000 a month to more than 1,400.
However, the figure could be higher as many bodies are never found.
Most bodies are believed to be those of civilians caught up in the sectarian violence and have since been buried in unmarked graves.
Meanwhile, at least five people died on Tuesday after a car bomb exploded near mourners at a funeral in south-west Baghdad.
Iraqi police also found the severed heads of nine people in fruitboxes in the village of Hadid near Baquba, north-east of Baghdad.
Last week eight severed heads were found in the same region, authorities said.