Car bombs killed seven people in Mahmudiyah and five around Baghdad, the Chinese news agency Xinhua reported.
Police said they found the dumped bodies of three men and one woman who had been shot in the head.
The attacks continued a surge of violence in the past month that left more than 1,000 people dead, the highest monthly figure in nearly six years, Middle East Online reported.
Notable deaths of 2014 [PHOTOS]
India's satellite approaches Mars