YANGON - Myanmar authorities exhumed the body on Wednesday of a journalist killed in military custody, and one rights activist said the body bore what he thought were marks of torture.

Freelance journalist Par Gyi was detained by the army on Sept. 30 after photographing clashes between the military and the rebel Democratic Karen Benevolent Army (DKBA). The Myanmar-based Assistance Association for Political Prisoners (AAPP) says he was killed on Oct. 4.

The AAPP has disputed a statement by the military that Par Gyi was shot when he tried to steal a gun from a soldier and escape after being detained because he was a member of an ethnic Karen rebel organisation.

President Thein Sein last week responded to calls by rights groups and the United States government and ordered Myanmar's National Human Rights Commission to carry out an investigation into Par Gyi's death.

Human rights activist Nay Myo Zin said about 100 people, including military and police officers, watched as the body was exhumed in Kyaikmayaw township, in eastern Mon state near the frontier with Thailand.

"We didn't see any gunshot wound on the lower part of the body, but the head was found full of cracks and wounds, with broken teeth and jaws," he said, suggesting the injuries looked more like those sustained from torture than someone who was shot while running away, as the military have said.

A team of doctors has been assigned to carry out a post-mortem, and the commission will begin interviewing people as part of its investigation, said Nyan Zaw, a member of the commission who witnessed the exhumation. It was not immediately known when the results of the post-mortem would be available.

"We'll ask everybody who we think is necessary to answer in connection with this case," he said by telephone.

The incident comes at a sensitive time for Myanmar as the government prepares to host U.S. President Barack Obama at a regional summit in a week. The U.S. State Department has called for a transparent investigation into the death of Par Gyi, a former democracy activist who once worked as a bodyguard for opposition leader Aung San Suu Kyi.

Speaking to reporters on Wednesday in Myanmar's largest city, Yangon, Suu Kyi said many people will be watching to see if the investigation is carried out according to the law. "Not only in our country, but also people outside the country are watching to see how they handle this case," she said.

The military claimed Par Gyi was an information officer for an obscure insurgent group called the Klohtoobaw Karen Organisation.

Par Gyi's wife, Than Dar, a prominent women's activist, denies her husband was a member of any military organization. She says she suspects he died while being tortured, leading the military to bury his body in secret. She says the DKBA has also issued a statement denying he was connected to any rebel military organisation.

Various rebel groups have battled Myanmar's central government since shortly after independence from Britain in 1948. While the reformist civilian-led government has struck ceasefires with almost all factions, clashes often flare up, undermining the government's goal of signing a national ceasefire agreement before next year's elections.