BAGHDAD — Gunmen wearing Iraqi army uniforms abducted and killed at least 13 people in a village west of Baghdad, in what some described as revenge against Sunnis who helped fight al-Qaida, Iraqi officials said Monday.

The exact motive for the attack was unclear, but it could be a case of insurgents killing locals allied to the central government or an internal struggle among the region's fractious tribes ahead January's elections.

The victims included a member of the country's main Sunni political party and several of his relatives, said party official Mohammed Iqbal, suggesting a political motive to the attack.

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

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.

The mayor of Abu Ghraib, Shakir al-Zubaie, told The Associated Press that none of the people killed in the nearby village of al-Saadan 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 the deaths as a revenge attack against people who had helped stabilize the area.

"The IIP condemns this ugly crime and it is a worrisome indication that the situation might be deteriorating and it represents a revenge against the people who had helped stabilize the area," the statement read. "This heinous crime reminds us of the crimes committed during the past years of insecurity. The people behind this crime are aiming at seeding insecurity and turmoil in the area."

All 13 had been shot in the head, possibly execution-style, as well as elsewhere in their bodies, said Waleed al-Zubaie of the police.

All the local officials confirmed the gunmen were wearing military uniforms.

A Defense Ministry spokesman was not immediately available for comment.

Maj. Gen. Qassim al-Moussawi, head of Baghdad's Operations Command, said in a statement that officials are looking into the 13 deaths and suspect it may have been a tribal dispute.

Speaking to the AP later, he said officials are looking for 10 suspects believed to be involved in the incident, who live in the area.

At least seven bullet-riddled bodies were admitted to the Abu Ghraib hospital, said Mohammed Sadoun, an official there.