A Cambodian military police officer has been arrested in connection with the brutal killing of a journalist who exposed illegal logging activities, police said.
Hang Serei Oudom, a reporter at local-language Vorakchun Khmer Daily, was found in the boot of his car in northern Ratanakiri province on Tuesday.
He appeared to have suffered axe blows to his head, according to police, the latest death in a country where environmental activists regularly face threats.
"We arrested a military police officer named Ean Bunheng on Thursday," interior ministry spokesman Khieu Sopheak told AFP on Friday, adding that the suspect was understood to have met the victim on Sunday, the night he disappeared.
Police found "a blanket stained with blood" at the suspect's house -- which is also a karaoke parlour -- and discovered the victim's shoes nearby, the spokesman said.
Several other people who were seen drinking with the 44-year-old journalist at the karaoke venue that night have also been questioned, but the spokesman declined to provide further details.
Pen Bonnar, of rights group the Cambodian Human Rights and Development Association, told AFP those questioned included the suspect's wife and the son of a provincial military police commander who Oudom had accused of wrongdoing in his reporting.
In his final article on September 6 Oudom alleged the son, who is also a military policeman, of smuggling logs in military-plated vehicles and extorting money from people who were legally transporting wood.
Local activists said fellow reporters had recently expressed fears for Oudom's safety because of his exposes.
Reporters Without Borders on Thursday called for a thorough investigation and urged police to explore links between his murder and his coverage of environmental issues.
The murder comes less than six months after prominent environmentalist Chhut Vuthy was shot dead by a military policeman after he refused to hand over pictures showing logging in southwestern Koh Kong province.
Rampant 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 its haste to develop the impoverished nation, the Cambodian government has been criticised for allowing well-connected firms to clear hundreds of thousands of hectares (acres) of forest land -- including in protected zones -- for everything from rubber and sugar cane plantations to hydropower dams.