The Tonga police have confirmed the death of a New Zealand policeman Kali Fungavaka at Vaiola Hospital this evening.

Assistant Police Commissioner Viliami 'Unga Fa'aoa said that he was notified from the hospital that Kali died at 18:35 hours.

"The body will remain at Vaiola for a pathologist to determine the cause of death," he said.

Three people, including two Tongan police constables, remain in custody following an incident on the night of Friday August 17 when the Kali Fungavaka was arrested and taken to a police cell.

The two Tonga police were arrested for allegedly assaulting the victim before he was put into the cell.  An inmate of the cell has been charged with causing grievous bodily harm of the victim, who underwent surgery for head injuries.

"Now that the circumstances have changed since the victim died we will look at other potential charges which are manslaughter by negligence or murder," he said.

"It depends on the evidence but with one of the accused they will consider an appropriate change from grievous bodily harm to either manslaughter or murder."

When asked if the police officers would also be investigated for murder, 'Unga said, "it depends on the evidence, but I don't believe so."

He said that it was very unfortunate that this has happened. "Whoever did this no matter who they are will be prosecuted the same as any other person, because everyone has to answer to the law," he said.