Venice has become the first city in the world to introduce a tourist entrance fee as it tries to tackle overcrowding.

Any visitor who is not staying the night must pay a €5 (£4.29) entry fee online before entering the city on April 25, which is an Italian national holiday and the first of 29 days this year when visitors are being charged to get in.

Although there are no turnstiles at the city gateways, inspectors will be making random checks and issue fines of between €50 and €300 (between £43 and £257) to anyone who has failed to register.

“No one has ever done this before,” Luigi Brugnaro, the mayor of Venice, told reporters ahead of the experimental measures being introduced. “We are not closing the city... we are just trying to make it liveable.”

Some 20 million people visited Venice last year, a city official said, with about half of them staying overnight in hotels or holiday lets – dwarfing the city’s population of 49,000.

Venice narrowly escaped being placed on Unesco’s “World Heritage in Danger” list last year partly because the city was addressing concerns that its ecosystem risked being overwhelmed by tourism.

As well as introducing the entry charge, the city has also banned large cruise ships and announced limits on the size of tourist groups.

“The phenomenon of mass tourism poses a challenge for all Europe’s tourist cities,” said Simone Venturini, the council official responsible for tourism and social cohesion.

“But being smaller and more fragile, [Venice] is even more impacted by this phenomenon and is therefore taking action earlier than others to try to find solutions,” he said.