MOSCOW, Russia (CNN) — Young women in bright miniskirts and high heels line up to sell themselves in the dingy back streets throughout the Russian capital. Moscow's illegal flesh markets are flourishing, with up to 30 women at each pickup point, or tochka, standing in order of price for the night.

Customers light up the lines with their car headlights and are asked to pay between $100 and $700 for a woman.

Aid workers for groups fighting for women's rights say Moscow is witnessing a surge in prostitution, including forced prostitution, as a result of Russia's booming economy.

They say thousands of young women are made to work as sex slaves on the city's streets, unable to escape from the ruthless and violent criminal gangs who traffic them….

…..Russian police acknowledge that human trafficking for sexual exploitation is a major problem, saying they do what they can to fight it by raiding brothels suspected of forced prostitution and arresting gang members who run them. But the problem, they say, lies elsewhere.

"First of all, we have virtually open borders, and badly controlled migration flows from nearby countries," said Alexander Krasnov of Russia's Interior Ministry Police.

'A large proportion of us will be suffering from general weather blues and will feel resentful and frustrated. Unless conditions improve or we have an Indian Summer later this autumn, more and more people are going to feel generally down.

'Depression is brought about when we feel we cannot control a situation and that is exactly the situation here  -  unless we go on holiday there is nothing we can do.

'In addition it is fair to say that people will not have ventured outside very much this summer so they will only have been exposed to artificial light which does not provide the same chemical reactions as sunlight. It's very important that we all put on their sou'westers and head out into the rain just to get a small amount of natural light.'

Alison Kelly, spokesman for the mental health charity Mind, said: 'We have recently carried out research that showed there was a direct link between people feeling good about themselves and how much exercise they undertake outside in the sunlight.

'If conditions prevent them from doing this then it is fair to say that more people will be feeling gloomy.

People have had hardly any opportunity to go outside and enjoy barbecues and socialise outdoors so they have been inclined to stay inside and this will reduce their mood.'