Iraqi security forces found 53 corpses, blindfolded and handcuffed, in a town south of Baghdad early on Wednesday, local officials said.
They said the bodies had been left in the mainly Shi'ite Muslim village of Khamissiya, about 25 km (15 miles) southeast of the city of Hilla, near the main highway running from the capital to the southern provinces.
The head of the provincial council, local police and the governor's office all confirmed the discovery of the bodies, but had no immediate information on the identity of the dead, who appeared to have been killed execution style.
The bodies were found at 2:00 a.m. (2300 GMT) on Wednesday, they said.
Sunni Islamist fighters seized control of large parts of northern and western Iraq last month, sweeping towards Baghdad in the most serious challenge to the Shi'ite-led government of Prime Minister Nuri al-Maliki since the withdrawal of U.S. forces in 2011.
Fierce fighting between the insurgents and the army, backed by Shi'ite militias, has raised fears of a return to the devastating sectarian bloodshed which peaked in Iraq in 2006 and 2007.
Sunni militants have been carrying out attacks around the southern rim of Baghdad since the spring. In response, Shi'ite militias have been active in the rural districts of Baghdad, abducting Sunnis they suspected of terorrism, many of whom later turn up dead.
According to medical officials, the number of unidentified bodies found around Baghdad have risen steadily since the beginning of the year.