Soldiers in an area of north-eastern Cambodia where illicit logging and smuggling are rife are reported to have killed a forest protection ranger, a military police officer and a conservation worker in apparent retaliation for their seizure of equipment from illegal loggers, officials have said.

Keo Sopheak, a senior environmental official in Mondulkiri province, said the three-person team was attacked late Tuesday afternoon after patrolling in the Keo Seima wildlife conservation sanctuary. He said the dead civilian was a Cambodian employee of the New York-based Wildlife Conservation Society.

The three are the latest victims of an alarming trend in recent years, the murder of environmental defenders by parties seeking the financial exploitation of natural resources. Roughly 200 activists have been killed worldwide in each of the past two years, according to the UK-based watchdog group Global Witness.

“The three were killed not by robbers or a guerrilla group but they were shot by government armed forces who backed the illegal timber cutting,” Sopheak said. The conservation team had earlier confiscated chainsaws and motorcycles from some Vietnamese logging illegally, he said.

WCS has named the victims as Thol Kna, Tern Soknai and Seng Vattana. Photograph: WCS Cambodia

A copy of a report sent by Mondulkiri police chief Ouk Samnang to national police chief, Neth Savouen, identified three border security officials whom it said had shot and killed the conservation team. Cambodian security forces are known to collaborate with illegal loggers who smuggle the wood to neighbouring Vietnam.

The Keo Seima sanctuary has valuable timber and is a habitat for many wildlife species. The multimillion dollar illicit trade in wood plagues much of south-east Asia, with China being the major market and transit point. The trade is vast even though the region has suffered heavily from deforestation for several decades.

In early 2016, Cambodia established a special committee to crack down on the smuggling of logs to neighbouring Vietnam, and tough-talking prime minister, Hun Sen, said he authorised helicopters to fire rockets at smugglers of illegally cut timber, but there has been no public evidence of a major crackdown.

Sopheak and other officials said a special committee has been established to investigate Tuesday’s attack.