Amsterdam's sex workers Thursday protested against the transfer of their famed red light district to an out-of-town "erotic center", in what is seen as part of a battle for the city's soul.

Many wearing masks to shield their identity, dozens of sex workers marched through the streets towards City Hall, one carrying a banner saying: "If sex workers are not to blame, then why are we being punished?"

Mayor Femke Halsema wants to uproot the red light district and move it out of town to a purpose-built "erotic center", aiming to rid Amsterdam's image as a "sin city" while reducing the number of tourists and petty crime in the area.

But she has found herself up against local residents who do not want the new center on their doorstep, as well as sex workers who feel they are scapegoats for the criminals and crowds surrounding their neon-lit booths.

Halsema has long opposed the centuries-old red light district, known as De Wallen, with its neon-lined windows in canalside houses where sex workers stand waiting for customers.

The city council has earmarked three possible sites for the erotic center, which would have 100 rooms for sex workers.

One sex worker who identified herself only as Lucie dismissed the idea as "one big gentrification project".

"It's mainly about combatting the crowds in De Wallen, but that is not the sex workers' fault so I don't see why we should be punished for it," said Lucie, who declined to give her last name.

'We just don't want it'

Even the European Medicines Agency has been caught up in the controversy after it emerged one possible site for the erotic center was near its headquarters.

The EMA voiced outrage, saying it could affect the safety of people working late at the office.

More than 20,000 have signed a petition against the transfer of the booths, calling instead for better crowd control in the area and greater police surveillance, especially at night.

Mariska Majoor, a former sex worker who now advocates for their rights, said the protests against moving the district had already been going for 16 years and that City Hall kept changing the goalposts.

"The authorities had a plan to reduce part of the brothels already in 2007. Then it was because of the fight against people trafficking and abuse and now it's about the fight against mass tourism," she told AFP.

Moving the red light district is Amsterdam's latest effort to transform its image as a party capital.

It has also launched a "stay away" campaign to discourage stag nights and boozy tourists, which caused a stir in Britain after the council said it would start by targeting British men aged 18 to 35.

The demonstration also attracted out-of-town locals who might suddenly find themselves living next to the new "erotic center."

Cynthia Cournuejouls, a 42-year mother living to the south of the city, told AFP: "We don't want the biggest brothel in Europe in our neighborhood."

"We just don't want it. We want to keep it here."