A pro-democracy activist group claims one of its members, an Australian man named Tran Hiep, has been kidnapped by a foreign government while working overseas.

Mr Hiep, 50, from Melbourne, has been out of contact with friends, colleagues and loved ones since September 18.

He was travelling alongside 52-year-old Nguyen Duc Thuan, his Norwegian-Vietnamese colleague.

Mr Hiep was visiting Cambodia in his capacity as an activist for US-based pro-democracy group Viet Tan when his relatives in Australia lost contact with him.

Viet Tan have since claimed Mr Thuan and Mr Hiep were abducted by operatives of the Vietnamese government while still inside Cambodia, before then being illegally taken back across the Cambodian border into Vietnam.

“Viet Tan strongly condemns the abduction of two of its members in Cambodia and the fabricated charges issued by the Vietnamese communist authorities to cover up an act of transnational repression,” a statement from the group reads.

“Viet Tan affirms that the two members had no intention of entering Vietnam. After abducting Duc Thuan, a Norwegian citizen, and Tran Hiep, an Australian citizen, the Vietnamese communist authorities claimed that the two men had ‘illegally entered from the Cambodian border’.

“This is a blatant fabrication intended to conceal the fact that the Viet Tran members were abducted in Cambodia and forcibly taken to Vietnam.”

It is understood Mr Thuan and Mr Hiep were in Cambodia to meet with pro-democracy activists from Vietnam.

Viet Tan was formed in the aftermath of the Vietnam War by elements of the country’s fractured pro-democracy movement.

Both DFAT and the Vietnamese government have been contacted by NewsWire.

Claims Aussie ‘kidnapped’ by foreign country