Amsterdam and the port of Rotterdam on Wednesday made face masks compulsory in certain busy areas including the Dutch capital's Red Light district, as coronavirus infections showed a worrying spike.
The new measures come as the number of infections doubled in a week in the country, where more than 55,000 people have now been infected and some 6,150 have died.
"We're starting this experiment because we're worried about the increasing number of coronavirus infections," the Amsterdam city council said.
"Face masks are compulsory in crowded and busy areas and where other measures didn't work or have adverse economic effects," it said in a statement.
Despite council workers handing out free face masks, a mobile van with loudspeakers and police warning people, not everybody heeded the new measures, especially in the Red Light district.
Many walked around maskless and law officers said they were only warning people and not handing out fines.
"Unfortunately it fits in a bit with the profile of the city," said one Red Light District resident who asked not to be named and who was wearing a multi-coloured mask.
"Everything is possible and nothing is ever enforced here," he said.
"We are from Germany and I was like... 'what the hell' when I saw people were not wearing masks where its compulsory," added Soph Schaller, 20, a nursery school teacher from Cologne in Germany.
"There we are quite used to it and have been wearing masks for a while now," she told AFP.
In the port city of Rotterdam, police stopped a group of demonstrators who wanted to march against the enforced wearing of face masks, Dutch media said.