Fiji songwriter allegedly bashed by officers after row with PM Frank Bainimarama over song rights

Fijian authorities must fully investigate allegations army officers bashed a man who sent angry text messages to prime minister Frank Bainimarama, Amnesty International says.

The human rights group said it has credible information four army officers assaulted 60-year-old teacher Josefa Bilitaki at his home last week.

It said the man earlier had an angry exchange of text messages with Mr Bainimarama, alleging that his songs were used without permission during the recent election campaign.

Mr Bainimarama's Fiji First Party won 59.2 per cent of the vote in last month's election.

Mr Bilitaki's daughter said four army officers appeared at her father's house on Friday night to question him.

She said her father was then taken to another location and was punched by the officers.

She said he had some bruises and a cut lip and is in hospital being treated for health issues not related to the alleged bashing.

Fiji's police commissioner Ben Groenewald released a statement saying the incident was being investigated.

He said a "task team" visited Mr Bilitaki and took him to a police station for the "alleged offence of annoyance".

Commissioner Groenewald said Mr Bilitaki fell ill the next day and was taken to hospital with high blood pressure.

"I visited him today and he is in a satisfactory condition. The allegation of assault against Mr Bilitaki is void of all truth," he said in the statement.

"I am urging people not to jump to conclusions [based] on what they read on social media.

"The case is under investigation and will be submitted to the Office of Director Public Prosecution once completed."

He said the interference of military personnel in policing issues was "unacceptable" and would be discussed further.

Amnesty International's pacific researcher Kate Schuetze said Fiji needs to show it is taking human rights issues seriously.

"Change within security forces doesn't happen overnight. But what we need to see is a clear indication from the top that these sorts of cases will be investigated," she said.

"That people, if found to be involved in them, will be held accountable and that anyone that orders these attacks will also be held responsible."

Allegation consistent with previous reports: Amnesty

Ms Schuetze said the allegation is consistent with previous reports of assault by military and police authorities in Fiji.

Last month, Vilikesa Soko died in custody after police arrested him in August in relation to the robbery of a foreign exchange store.

An autopsy revealed he died from massive internal injuries. Four police officers have been suspended over his death but no charges have been laid.

That case followed the circulation of a video last year showing what appeared to be prison officers torturing two prisoners.

One man was savagely beaten with batons and metal bars while handcuffed.

The other was set upon by a dog as its handler urged the animal on.

At the time Mr Bainimarama said he would stand by the officers in the video and argued they were just doing their job.

No-one has been arrested in relation to that case.

Fiji's military head Brigadier Mosese Tikoitonga has not responded to the ABC's request for comment.