Thai forces shot dead 38 Cambodians in the first half of this year for illegally crossing the border to log for valuable timber, according to the Cambodian authorities.

A further 10 Cambodians were injured in incidents with Thai border forces and 194 were arrested, though not all of them on suspicion of illegal logging, the Cambodia-Thailand Border Relations Office said in a report dated August 12.

The number of fatalities dwarfs the toll last year when around 11 alleged Cambodian loggers were reported killed over a 12-month period, according to statistics collected by local rights group ADHOC.

Nicolas Agostini, a technical assistant at ADHOC, blamed the spike in deaths on a growing number of frontier residents willing to risk their lives to escape poverty.

"The levels of poverty in the border provinces are quite high and people are desperate," he told AFP.

Cambodian loggers are routinely caught sneaking into Thailand, often in search of rosewood, which fetches thousands of dollars per cubic metre and is in strong demand in China and Vietnam.

Years of rampant illegal felling in Cambodia have devastated the country's own luxury timber stocks.

Cambodian officials, including Prime Minister Hun Sen, have repeatedly urged Thailand to arrest trespassers instead of firing at them, while Bangkok says its troops are acting in self-defence against armed Cambodians.

Agostini urged Thai authorities to launch "meaningful investigations" into the killings.

"We are really concerned that Cambodian loggers may have been shot on sight," he told AFP. "The use of firearms is only justified as a last resort."

Cambodian officials were not immediately available for comment while a Thai army spokeswoman said she was unable to confirm the death toll.

The border between the two countries has never been fully demarcated, in part because it is littered with landmines left over from decades of war in Cambodia.