SAINT PETERSBURG • President Vladimir Putin recently quipped that Russian prostitutes are "the best in the world" as he dismissed unsubstantiated rumours that Moscow had incriminating evidence on his American counterpart Donald Trump.

But the reality is that Russian sex workers operate in a hidden world outside the law and out of sight - making them doubly vulnerable to infection and abuse, as Agence France-Presse (AFP) journalists found out after being granted rare access to an illegal brothel.

In a grand Stalin-era tower block in the north-western city of Saint Petersburg, a woman in her 30s opens the door of an apartment and introduces herself as Inna, the receptionist of this so-called salon.

"Go into the kitchen. Nadya's working, but Nastya and Madina are in there," she says.

Nastya, 31, and Madina, 20, are wearing T-shirts over flimsy nighties and are drinking tea in the small kitchen.

The women only agree to speak to AFP as they trust an accompanying activist from the only non-governmental organisation in Russia that helps sex workers called Serebryanaya Roza, or Silver Rose.

The activist, Ms Regina Akhmetzyanova, spends her evenings going to such clandestine brothels to hand out condoms and offer sex workers HIV tests.

This is particularly important for prostitutes as infection rates in Russia are growing, with more than 103,000 new cases identified last year, up 5 per cent from the previous year. The real total is likely to be significantly higher.

Prostitutes admit they are under pressure to have unsafe sex.

"They've beaten me and threatened me with a knife, forced me to do it without a condom," said Madina, who is from Uzbekistan and speaks only basic Russian.

While prostitution is illegal in Russia, it is punishable by a fine of just 1,500 roubles (S$36).

Pimps theoretically face up to three years in jail, but are harder to convict since this requires the police to track financial flows.

Activists say this legal ban is often used by the police as an excuse not to investigate crimes against sex workers.

"We're told (the) profession doesn't exist, that means (sex workers) don't exist for the government on the one hand, but on the other hand, since (prostitution) is an administrative offence, sex workers are totally defenceless and without rights," says Silver Rose's founder Irina Maslova.

AGENCE FRANCE-PRESSE