Vietnamese asylum seekers at the Christmas Island Immigration Detention Centre say members of the group were bashed and injured during a targeted attack on Friday night.

Three separate sources told the ABC they were contacted by Vietnamese asylum seekers on the island, who said they were mobbed by a group of Iranian detainees.

The Darwin Asylum Seeker Support and Advocacy Network (DASSAN) said two Vietnamese asylum seekers from the centre contacted it in separate private messages on Facebook the next day.

One of the asylum seekers told the advocacy group up to 30 people were beaten.

"Somebody [was] hurt in [the] head, somebody hurt in [the] arms and legs, in the back," the asylum seeker wrote in the Facebook post.

The refugee advocate asked about the response of Serco, the company responsible for security at detention centres.

"They did not care what happened with us. The police, they [said] 'If Serco agreed they [would] be going in detention and checking', but Serco did not agree," the asylum seeker wrote.

A Vietnamese advocate in Australia - who did not want to be identified - said one of the Vietnamese detainees called him around midnight.

Facebook discussion of the alleged incident. ( ABC: Supplied )

"He mentioned very clearly that the Iranian people came [during dinner time] and they smashed up all the tables, messed up the food and chased them," he said.

"They said they beat them very hard."

A refugee advocate and Vietnamese man from Perth, Nam Pham, told the ABC he was called on the Saturday morning by a Vietnamese asylum seeker at the facility.

"He contacted me reporting the violence in the compound next to him and many of his friends had been injured, beaten up by the other asylum seekers at the centre," Mr Pham said.

"He said he tried to contact the police, but he said he either couldn't get through or they couldn't come in to help.

"He said basically Serco people were afraid of the violence going on there, so the [Vietnamese asylum seekers] got beaten up.

"They had to stay outside their compound for the whole night, they were too afraid to go back into their compound."

A spokesman for Immigration Minister Scott Morrison denied the claims by advocates.

"Claims referred to by asylum advocates in relation to the incident on Christmas Island are grossly inaccurate," the spokesman said.

"The incident was dealt with in the usual manner and the centre returned to normal operation."

Vietnamese detainees have been attacked before: advocates

DASSAN spokesman Peter Robson said Vietnamese asylum seekers had been facing threats, intimidation and assaults at the Christmas Island facility in separate incidents for weeks.

Discussion on Facebook of the alleged incident. ( ABC: Supplied )

He said some of the Vietnamese detainees were told they were being targeted because they arrived before the July 19 processing cut-off and would not participate in protests.

"We understand that it's got something to do with tensions with the fact that most of the Vietnamese who are there arrived before the cut-off date when they could still apply for asylum," Mr Robson said.

"We understand many of them have been seriously injured, threatened with rape and in some cases some people have been allegedly sexually assaulted.

"Our understanding is that the Vietnamese asylum seekers are asking to be moved to a safer place, but the authorities haven't done so."

The advocacy group said it had made contact with a Vietnamese man transferred to a Darwin detention centre in the past two weeks who said he was sexually assaulted at the Christmas Island detention centre.

They said the man was severely traumatised and they had urged him to seek counselling.