Three suspected illegal timber traders were charged on Tuesday over the murder of a Cambodian journalist investigating illegal logging, a prosecutor said.

Taing Try, 48, was shot dead early on Sunday, according to police in the northeastern province of Kratie.

He is the second journalist probing Cambodia's lucrative trade in illegal timber to be killed in two years.

A former soldier, a policeman and a military police officer -- all suspected log traders -- were arrested several hours later.

The 32-year-old ex-soldier was charged with murder, Thuch Panchak Santepheap, deputy prosecutor at Kratie provincial court, told AFP.

He said the military police officer was charged as an accomplice because his gun was used to kill the journalist, while the third man was charged for not filing a murder complaint.

Taing Try was killed while he and several other reporters were investigating illegal logging -- which is widespread in the impoverished nation.

The Khmer Journalists for Democracy Association said he had been repeatedly accused of extorting money from timber traders in the past -- although there was no evidence to back up the allegations.

Environmental activists regularly face threats in Cambodia, where land grabbing has become a major source of tension and illegal logging is rampant.

Unchecked illegal logging contributed to a sharp drop in Cambodia's forest cover from 73 percent in 1990 to 57 percent in 2010, according to the United Nations.

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, Hang Serei Oudom -- a reporter at local-language Vorakchun Khmer Daily -- who also exposed illegal logging was found dead in the boot of his car in the northern province of Ratanakiri.

A Cambodian court acquitted a military policeman in 2013 over Oudom's brutal killing.