Fiji's People's Democratic Party is calling for an independent investigation into the death of Vilikesa Soko, who is alleged to have been the victim of police brutality.
Mr Soko's father says his son was beaten by police after he was arrested in a suspected gang-related robbery in Nadi.
He died last week in Lautoka Hospital.
The party's leader, Felix Anthony, has distributed copies of Mr Soko's medical report, which states he was the victim of an alleged assault and multiple traumatic injuries contributed to his death.
"The medical report clearly states that this man has been brutally killed. What we want from the Commissioner is an independent investigation and not an internal investigation because we've had many internal investigations in the police and nothing has come forward to the public and nor has any action been taken on people responsible."
Mr Anthony says it is the eleventh such unexplained death and Fiji's Prime Minister has much to answer for.
A Fiji human rights watchdog has called for the suspension of police officers involved in the arrest of Vilikesa Soko.
The chair of the NGO Coalition on Human Rights, Shamima Ali, says she welcomes the Police Commissioner's statement that immediate investigations would be carried out, but she says the probes must be done with complete transparency.
She says that should involve suspending the officers from duty even though they're entitled to be presumed innocent until proven guilty..
Ms Ali says this would enable a fair and impartial investigation without any appearance of bias or potential for interference.