Yangon, Myanmar: Myanmar police on Tuesday said they had arrested three people over the murder of a local journalist known for his investigations into illegal logging and brothels.

Eleven Media reporter Soe Moe Tun's battered body was found last month on the side of a road in Monywa, northwest of Mandalay.

Myanmar ended official censorship in 2012 after the military junta ceded power, but journalists still face intimidation for investigating controversial topics. 

At least four reporters have been killed with impunity in Myanmar since 1999, according to the New York-based Committee for the Protection of Journalists. 

Local media sources said Soe Moe Tun had reported on the mining industry, illegal logging and the growth of karaoke lounges fronting for brothels before his death.

Thein Swe Myint, an officer from Monywa police station, said authorities had arrested three suspects after questioning some 40 people over the murder.

"First we arrested two people from a local KTV (karaoke) operator and we have arrested another one who used to be a logging truck driver," he told AFP.

Saigang region, where Soe Moe Tun worked, is a hub for mining and logging of Myanmar's prized teak wood. 

Much of the timber is smuggled out of the country to India in a vast illegal trade thought to be worth billions of dollars. 

Advocacy groups say journalists covering the industry are increasingly facing intimidation for their work.

At least 10 reporters covering environmental issues have been killed in South and Southeast Asia since 2010, according to Reporters Without Borders.

Several months ago local Myanmar reporter Tin Zaw Oo was forced to move after his family was threatened by illegal loggers, said Myanmar Journalists' Network.

Soe Moe Tun's wife, Khin Cho Lett, said she hoped his killers would be brought to justice. 

"My husband was killed very cruelly," she said. "I am waiting for the truth."