Ten people, including a soldier, have been arrested over the murders of a forest ranger and a policeman who were investigating illegal logging in Cambodia, officials said on Friday.

Probes into the lucrative trade are steeped with risk and several high-profile killings of activists trying to expose the rampant spread of logging have blighted the kingdom in recent years.

Forest ranger Sieng Darong, 47, and police officer Sab Yoh, 29, were shot dead on Saturday during a patrol of the protected northwestern Preah Vihear forest in an attack which also wounded another ranger.

The pair were "gunned down by cold-blooded killers with high powered weapons as they slept during an overnight patrol", Ross Sinclair, director of the Wildlife Conservation Society (WCS) in Cambodia said in a statement.

The men were killed hours after they confiscated chainsaws from an illegal logging site, according to the WCS, which has patrolled the area since 2000.

On Friday Colonel Khat Hun, deputy chief of Preah Vihear provincial police, told AFP that 10 suspects, including a soldier, who were believed to be involved in unsanctioned logging in the forest, had been arrested and sent to court over the murders.

He declined to give further details.

Lor Chann, a local coordinator for Cambodian rights group Adhoc, said loggers conducted the attack "in retaliation against the pair" for cracking down on the illicit timber trade.

In the last few decades a surge in illegal logging has contributed to a sharp drop in Cambodia's forest cover, which fell from 73 percent in 1990 to 57 percent in 2010, according to the United Nations.

Questioning the profitable trade has left a string of fatalities in recent years.

Last year Cambodian journalist Taing Try was killed while investigating illegal logging in northeastern Kratie.

A former soldier, a policeman and a military police officer -- all suspected log traders -- were arrested and charged over the murder.

In April 2012 prominent environmentalist Chhut Vuthy was shot dead in a remote forest by a military policeman after he refused to hand over pictures showing logging in the southwestern province of Koh Kong.

Less than six months later a reporter at a local-language newspaper who also exposed illegal logging was found dead in the boot of his car in the northern province of Ratanakiri.