PHNOM PENH (REUTERS) - Cambodian Prime Minister Hun Sen admitted an "unintentional mistake" on Monday (Feb 7) in taking credit for helping to free an Australian in Myanmar who the military government said was not being released.

Sean Turnell, an economic adviser to deposed Myanmar leader Aung San Suu Kyi, was arrested on Feb 6 last year, a few days after a coup, and is charged with breaching the Official Secrets Act, punishable by up to 14 years in prison.

Mr Hun Sen, as chair of the Association of South-east Asian Nations (Asean), had earlier said Turnell had been freed following his lobbying of Myanmar junta leader Min Aung Hlaing to let him go, at the request of Australia's Foreign Minister.

"In reality, the Australian national was not released," said Mr Hun Sen in a Facebook post late on Monday.

"The confusion is because of me getting information wrong, please forgive me for unintentional mistake."

Myanmar military spokesman Zaw Min Tun told BBC Burmese there were no plans to release Turnell.

A source close to Turnell had also told Reuters there was no news of his release.

Turnell's trial has yet to start. He is among about 11,000 people detained since the coup, said activists.

Mr Hun Sen has sought to engage Myanmar's generals, despite Asean concerns about legitimising their rule.

He has repeatedly pressed the military to deliver on commitments with Asean to end hostilities and allow dialogue with all parties, including the ousted government.

A senior Cambodian official told Reuters on Monday that the junta boss had agreed to let an Asean special envoy meet some members of Suu Kyi's party.