The 77 Chinese nationals deported from Fiji by uniformed Chinese police in August were sex workers, Background Briefing has been told, in a challenge to official claims they were involved in an online gambling fraud ring.

The ABC understands the deportees were mainly young women brought to Fiji to service the Chinese diaspora, but the Fijian government has refused to confirm or deny these claims

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Footage shows police escorting the group from a gated suburban house in Nadi onto a bus.

Locals close to this house said the inhabitants were primarily young women aged between 15 and 19. One of those deportees was a young mother with a baby.

Aman Singh worries about the implications of the deportations for Fiji's sovereignty. ( ABC RN: Hagar Cohen )

In the two weeks before their deportation, witnesses reported seeing Fijian police officers moving in and out of the compound — including movements that resembled a changing of the guard, and overnight shifts.

According to one local, who asked not to be identified, several of the women had attempted to escape, but were chased and caught by local police.

Lawyer Aman Ravindra Singh said the deportation had serious implications. Previously, one of Singh's clients had complained about Chinese police officers working in the city of Lautoka, a move Singh describes as "a direct violation" of Fijian sovereignty.

"Under what law were [Chinese police] allowed to come and operate in Fiji?" he said.

"For mighty China to march its police up and down the streets of Fiji … This is so unreal. Almost like there had been an invasion of our jurisdiction."

When asked why Fijian police had not publicly released any information about the group's deportation, commissioner Sitiveni Qiliho — who also declined to comment for this story — said they had not wanted to jeopardise the operation.

Background Briefing contacted the office of Prime Minister Frank Bainimarama and the Chinese embassy in Suva to respond to allegations the deportees were teenage sex workers. None of those officials replied to our requests.

Business leader welcomes deportations

In 2016, according to statistics from Investment Fiji, half of all foreign investment in the Pacific Island nation came from China, making it the single biggest source of direct foreign investment.

The spending largely goes towards large infrastructure projects: including ports, bridges and utility companies. China is the second largest aid donor in the region, after Australia.

The Lowy Institute's Jonathan Pryke said it was part of a global push.

"China's just so large, and the Pacific relatively is so small… any sort of engagement can be seen as almost overwhelming," he said.

But the images of hooded deportees were welcomed by some locals, including Fijian-born Chinese business leader Dixon Seeto.

Mr Seeto, the head of the Fiji Hotel and Tourism Association, said the deportation sent a strong signal.

"If you had kept them here… you'd have to go through the whole rigmarole of the legal system," he said.

"It tells the criminal elements that we're not a dopey country … sooner or later, you get caught."

According to Dr Graeme Smith, a research fellow at the Australian National University, the deportations chiefly served a domestic propaganda purpose for the Chinese government.

"The message: we know this is a problem, but don't worry, we're doing something. We will go to the ends of the earth to track down these criminals," he wrote.

Underground sex work industry flourishing in Fiji

Prostitution is illegal in Fiji, though researchers have estimated it is widespread.

High unemployment and poor economic outcomes for women have led to a sex work industry that, on a per capita basis, is of a similar scale to Thailand's.

Human trafficking was implicated in one recent court case, involving two Thai women who came to Suva in August 2012 to work as masseuses for a Chinese man — a self-described "big Mafia" boss.

After coming to Fiji, the women were told they would be expected to have sex with clients.

While four men were initially convicted of sexual servitude and human trafficking offences, they later filed a High Court appeal, and were let off after Fijian prosecutors withdrew charges.

Locals are unwilling to talk to the media on the record, out of fear of police reprisal. But anecdotally it appears the sex work industry is flourishing, driven by Chinese workers and industry.

Netani Rika suspects a link between the deportations and the underground sex industry. ( ABC RN: Hagar Cohen )

Veteran Fijian journalist Netani Rika, the editor and publisher of Islands Business magazine, said the deportation of the 77 Chinese nationals this year was connected to Chinese investment in the region.

"There have been a large number of Chinese men brought into the country to work, and there's got to be a link between that, and bringing in women who will cater to their after-hours needs."

Rika, whose reporting has led to arson attempts on his house and stonings of his car, says there is no way of knowing the extent of Chinese crime syndicates' involvement in Fiji.

"We have evidence of Chinese massage parlours operating as brothels — the challenge is to find the link between those establishments and the people who've been taken out of the country," he said.