BAGHDAD — Gunmen in Iraqi army uniforms abducted and killed 13 people whose bodies were found Monday with gunshot wounds to the head, including a local leader of Iraq's largest Sunni party, which once helped fight al-Qaida.

Police played down the incident as tribal violence in an attempt to defuse sectarian tension, but the political connection suggests the killings could also have been the work of insurgents or rival Sunnis vying for power before January elections.

Violence has dropped sharply in Iraq over the past year, but politicians and security officials have warned in recent weeks of a possible spike in violence in the run-up to the national polls as insurgents look to undermine the government and destabilize the country.

Monday's attack took place at around 1:30 a.m. in the village of al-Saadan near the town of Abu Ghraib on Baghdad's western outskirts, Abu Ghraib Mayor Shakir al-Zubaie said.

Gunmen wearing military uniforms knocked on doors and ordered the residents to step outside, saying they wanted to search the houses for weapons. The assailants then handcuffed 13 men, shoved them into a minibus and drove off, al-Zubaie said.

All 13 men were later found in a nearby cemetery, killed execution style with a bullet to the head, said the mayor and police official Waleed al-Zubaie.

The killings are reminiscent of those that plagued Baghdad at the height of the sectarian bloodshed of 2006 and 2007, when men, sometimes dressed in police or army uniforms, snatched people from their houses at night before killing them and dumping the bodies.

Members of the Iraqi military have been accused in the past of taking part in such extra-judicial killings, but such uniforms are also widely available on the open market and have been used by insurgents in the past to conceal their identities.

Among the victims of Monday's attack was a member of the country's main Sunni political party and several of his relatives, said party official Mohammed Iqbal, suggesting a political link to the attack.

Violence has dropped dramatically in the predominantly Sunni regions of western Iraq after local tribes, many of whom had been involved in the anti-U.S. insurgency, banded together in so-called Awakening Councils and turned on their former allies, the militant group al-Qaida in Iraq.

Abu Ghraib Mayor Shakir al-Zubaie told The Associated Press that none of the people killed were members of the local Awakening Council but said some had fought against al-Qaida for a short time in early 2008.

The Iraqi Islamic Party condemned the killings, describing them as a revenge attack against people who had helped stabilize the area.