The United Nations and the European Union have urged the Cambodian government to carry out a speedy and independent investigation into the killing of a prominent environmental activist.
Chhut Vuthy, 43, was gunned down by a military policeman on 26 April as he was gathering evidence of illegal logging in a remote forest in a case that has sent shockwaves through the country.
Military police officials said the killer then turned his AK-47 assault rifle on himself, shooting himself twice in the chest –a claim that has been greeted with widespread scepticism.
"Despite the current lack of clarity about what exactly happened, we are very concerned that the killing of Mr. (Vuthy) marks the latest and most lethal in a series of gun attacks on human rights defenders in Cambodia," a spokesman for the UN High Commissioner for Human Rights said in Geneva.
"We urge the royal government to ensure that a full civilian judicial investigation proceeds speedily and with the utmost probity and independence," Rupert Colville said in a statement sent to AFP late on Tuesday.
The EU delegation in Phnom Penh also called for "a speedy, robust and independent" probe, according to a statement seen by AFP on Wednesday.
It added that the EU was "deeply concerned" about the incident in southwestern Koh Kong province "which casts a shadow over the government's and civil society's efforts to curtail illegal logging."
The government has set up a special committee to probe the shooting incident but it has already attracted criticism for including a high-ranking national military police official.
Campaigners say Cambodia has recently seen a rise in violence against citizens involved in land and labour disputes, resulting in a number of injuries, often at the hands of armed government security forces.
The UN human rights office in Phnom Penh said Chhut Vuthy's death marked its fifth investigation into the use of live ammunition against communities and human rights defenders since the start of the year.
Outspoken Chhut Vuthy, who inspired villagers to conduct forest patrols to monitor deforestation and illegal logging, is the most high-profile activist to have died since the 2004 daylight murder of union leader Chea Vichea.