SYDNEY (AFP) - Australia on Friday (Jan 25) said it was seeking access to a Vietnamese-Australian pro-democracy activist detained by security services on his return to Ho Chi Minh city.

Colleagues of Chau Van Kham in Australia told AFP on Friday they believed he was arrested on Jan 13.

The Australian Department of Foreign affairs confirmed it had "sought consular access to an Australian man detained in Vietnam" in response to query about Kham.

"For privacy reasons we are unable to provide further details," a statement said.

Kham's detention comes just days after an Australian blogger and author was arrested in China.

Kham, a retired businessman, was on a "fact-finding" mission to the country, entering via Cambodia, according to colleague Phong Nguyen.

Both men are members of the Viet Tan, an anti-government group that Hanoi considers a terrorist organisation.

Vietnamese authorities have accused the Viet Tan of "instigating violence", a charge the group rejects.

Colleagues said they did not know where Chau was being held. His wife and immediate family remain in Sydney.

"At the moment we don't know where he is," said Phong Nguyen. "He was aware of the risk, but he was determined to go on this fact-finding trip." The visit was designed to assess human rights in the country, Phong Nguyen added.

"We are mindful that the Vietnamese police have a history of framing peaceful activists with fabricated charges," he said.