Police have arrested 16 people during the first night of an operation targeting antisocial behaviour at Melbourne's St Kilda Beach.

Key points: People gathered at St Kilda beach in hot conditions

People gathered at St Kilda beach in hot conditions The 16 arrested face charges of drug possession, being drunk in public, criminal damage

The 16 arrested face charges of drug possession, being drunk in public, criminal damage Police also had to deal with brawling youths at the Chelsea foreshore

Another two people were arrested around the St Kilda light rail stop, and 123 were searched.

The crackdown follows a string of violent incidents on the beach. In the latest, police used capsicum spray in the arrest of two men on Saturday after a large group of young people allegedly assaulted and robbed a man.

In another last month, a group of youths attacked two men, smashing a bottle over one man's head and punching the other.

While the council-enforced drinking ban does not kick in until next week, the operation targeting antisocial behaviour began in earnest last night.

Those arrested face charges including drug possession, being drunk in public and criminal damage.

The operation coincided with hot conditions in the city — temperatures in Melbourne rose to 35 degrees Celsius at 5:00pm, and remained in the high 20s into the morning.

The police operation Sandsafe coincided with warm overnight conditions. ( ABC News )

The warm weather is expected to continue today, with a high of 38 forecast for the city.

Local area police inspector Jason Kelly said the operation on the beach involved "significant resources", including transit, mounted, plain clothes and water police.

"On these hot nights we get a lot of people down here to this iconic St Kilda beach and with large numbers of people also come some of the issues we've seen over the last month," he said.

"If you come down here and you commit a crime, you can expect to be arrested."

Just under 30 kilometres down the road, police also had their work cut out for them in Chelsea, where they were called to reports of brawling groups of youths.

The fight happened just after 6:00pm as temperatures peaked, but it took police another five hours to disperse the crowd that gathered at the Chelsea foreshore.

Police said they spent hours dealing with reports of unruly and antisocial behaviour.

One person was arrested for being drunk and two were fined for minor offences.