Police have opened a murder inquiry into the death of an opposition activist in northern Cambodia.

Seng Nak, 43, who had defected from the royalist Funcinpec party to the Cambodian National Rescue Party in 2012, was found dead in a rice field in Siem Riep province’s Puok district on May 6. Police were

alerted to his death at about 10pm, hours after he had reportedly left home to trap mice for food.

Authorities confirmed that Nak’s body had been found with bruising, but said a shortage of resources was preventing them from establishing why, and refused to speculate on the motives of his death.

“The investigation is ongoing, so I cannot draw any conclusions,” said Puok district police chief Tep Phumsen. “Because we are lacking experts to autopsy the body, we do not know why there are bruises on his head and his body,” he said.

Phumsen could not confirm reports Nak had been shot with a homemade firearm or any other type of weapon.

Nak originally switched political allegiances to run on the ticket of the Sam Rainsy Party for commune elections in Yeang commune in 2012 – an election he lost. When the party later merged with the Human Rights Party to form the CNRP ahead of national elections in 2013, Nak followed.

Police said Nak had originally gone out to the field where his body was found with his family on the morning of his death, but that they returned home when their tractor broke down. He subsequently returned despite heavy rainfall in search of food.

Nou Puthyk, Siem Reap provincial coordinator for human rights group Licadho, confirmed yesterday that the NGO’s representatives had seen the body and echoed the lack of clarity surrounding the case.

“Right now the local police and Licadho cannot yet determine the kind of dispute or find out the perpetrator,” Puthyk said.

Meanwhile, CNRP spokesman Yim Sovann urged the authorities to be rigorous in establishing the details behind the case.

“We want the government to do their investigation thoroughly and carefully, and we want them to make sure that they bring the perpetrator to justice,” he said.