A Japanese woman has become the fourth foreigner to die in unexplained circumstances since July in Fiji's tourist belt.

Two of the deaths have been of New Zealanders.

News of the death of Mami Nakamura, 27, has been kept out of the censored Fiji media since her body was found a week ago, but has now been disclosed as anti-military government blog sites revealed it.

Deaths of foreigners are subject to tight censorship as the Voreqe Bainimarama regime fears it will damage their multi-million tourist industry.

Former Greymouth hotelier Tony Groom was badly beaten in Nadi on July 8 and died eight days later. News of his death was suppressed until revealed in New Zealand, but Fiji police concluded he died of natural causes.

Auckland woman Chelsia Mary Lo, 33, disappeared off the back of a super-yacht in Blue Lagoon on June 13. Found dead on a village beach, she was cremated before her family learned of the death. The Fiji Government later said she was drunk at the time of disappearing.

On July 15 an American CEO, Don Nicholas, disappeared while learning to surf at the Intercontinental Hotel at Natadola, south of Nadi.

His body has not been found and his family have now posted a US$100,000 (NZ$121,000) reward for information on him.

In the latest death, Fiji Police say Nakamura was last seen leaving a language school, the Freebird Institute, in Nadi on August 31 at 2pm.

She told her friends that she was headed for a party at Wailoaloa Beach. Her decomposed body was found in mangroves on September 5.

The Fiji Sun today quoted military appointed Police Commissioner Brigadier-General Ioane Naivalurua saying investigations needed to be intensified and if there was any suspect or suspects, they needed to be brought to justice.

A post mortem could not establish the cause of death because of the advanced stage of decomposition her body was in.

He said the woman's family had cremated the body.

''Even though the family came and have cremated her, the case is not closed,'' he told the Fiji Sun.

''It is wrong to assume that even though there have been no suspects, and that she's now cremated that the case will be closed.

''That's wrong - a life has been lost, whether buried or not -we complete the process of investigation - we find the person or persons who are involved or took that particular life - we don't give up or rest until we discover the truth of what happened to Ms Nakamura.''