AMSTERDAM (AP) — Amsterdam's mayor says the city plans to raise the minimum age of prostitutes from 18 to 21 and force brothels to close in the early morning hours.

At a press conference Tuesday, Eberhard van der Laan said the decision follows from a desire to crack down on crime in the city's famed Red Light District and protect sex workers — mostly women — from abuse.

Van der Laan said the windows, where scantily clad sex workers try to entice customers, would be closed from 4 to 9 in the morning.

Prostitution was legalized in the Netherlands in 2006, and has been tolerated in Amsterdam for centuries, but the city has been tightening the rules and shuttered a third of the brothel windows in the period 2007-2009.