Dubai police arrested more than 20,000 beachgoers over the last two years for a variety of offences such as pestering or filming sunbathers and swimming in the sea in underwear.

A total of 4,236 “violators and intruders” were caught this year so far, with some given fines or arrests, 7Days newspaper reported.

Brigadier Mohammad Rashid Al Muhairi, head of tourism security at Dubai Police, said undercover members of his force patrolled the beaches every day.

“Many people, especially Asians, come to the sea to monitor women on beaches,” Al Muhairi was quoted as saying.

“We warn these people first – but if he repeats it then we take him to the police station to make him sign a document that he won’t repeat the offence again. Some of them target women sunbathing and stand near them looking – or sometimes taking pictures or annoying them.”

The officer said that men swimming in their Y-front underwear were also warned for committing “inappropriate acts”.

“When they step out the sea, you can see through their wet, white pants,” he said. “We always inform companies to educate their labourers who commit such offences – and if they repeat them then we arrest them.”