Phạm Thanh Sơn was reportedly stabbed outside a Karaoke bar in Đồng Hới, local media has reported.
A former Manus Island detainee has reportedly been killed in a stabbing attack in Vietnam after he returned to his home country following a failed bid for asylum in Australia.
According to local media reports, Phạm Thanh Sơn was stabbed outside a karaoke bar in Đồng Hới, Quảng Bình Province about 10pm, Thursday, local time.
Local media said Mr Phạm was taken to hospital and later died. The stabbing is under investigation by police.
Refugee Action Coalition spokesperson Ian Rintoul told SBS News on Monday that Mr Phạm spent about five years on Manus Island but was returned to Vietnam in 2017.
He said "many, many people" on Manus were now mourning.
"Even though at the moment we don't know if there's any direct connection between his stabbing and his asylum application, the reality is he would not be in Vietnam if there was a proper procedure on Manus Island," Mr Rintoul said.
"It's one more tragic consequence of Australia's offshore detention regime and one more reason why we need that brought to a close."
The Refugee Action Coalition claims Mr Phạm fled Vietnam as he was wanted by police for taking part in protests.
Mr Phạm was allegedly planning to sue the Australian government over his time in detention.
A spokesperson for the Department of Home Affairs told SBS News it did not comment on individual cases.
Iranian journalist and author Behrouz Boochani, who remains on Manus Island, posted a tribute to his "friend" on Saturday.
"Yesterday we heard that one of our friends, who was on Manus with us and was deported by the Australian government to Vietnam, he was killed," Mr Boochani told SBS News.
"That man was waiting to get protection from Australia for years and years."
While Abdul Aziz, who is also on Manus, said Mr Phạm was "a wonderful man" and "a great friend".
"He suffered five years on Manus under the inhuman conditions," he said.
An ABC News article from February 2017 quotes the Vietnamese asylum seeker, who said he was "very scared" after being told he would be forcibly removed from the island.
"I don't know what will happen to me in the next few days," he told ABC News.
"If they deport me, who is responsible if the police arrest me and kill me in prison?"
Australia's offshore detention centre on Manus Island was deemed unconstitutional by a Papua New Guinea court and closed in November 2017, but hundreds of refugees still remain on the island.
The men, many of who are without travel documents, need to request permission to leave the island and must abide by a curfew which states they must return to the compound, where they were moved following the centre's closure, by 6pm and not leave again until after 6am.