Hun Sen made the admission while addressing a forum of business leaders and government officials, promising to increase screening of containers at the country’s borders from next week.
Cambodia aims to screen 100 percent of all containers imported and exported through its international checkpoints to fight against terrorism, smuggling and drug trafficking, Hun Sen said.
Only 60 percent are currently screened, according to the prime minister.
"We have to make sure that drugs won’t be taken out of Cambodia to other countries, and we also have to make sure that weapons won’t be smuggled out of Cambodia to other countries," he said.
"Because in past years, Cambodia used to be a place where weapons were taken to Sri Lanka for the Tamil group, to Philippines’ Mindanao island... and for the Karen in Myanmar. We have some documents about this," Hun Sen said.
The government has to date destroyed nearly 160,000 seized weapons, Hun Sen added.
Cambodia has been accused of being a major source of illegal weapons, arming rebel groups across Asia including the Tamil Tigers in Sri Lanka and militants in Indonesia’s Aceh province.
Cambodia, destitute after decades of war that only ended in 1998, is battling rampant smuggling and trafficking of goods including gasoline, cigarettes and consumer products, drugs and humans.