Riot Police have been called in to disperse teenagers at out-of-control Airbnb parties in New South Wales twice in recent times, with the company cracking down on New Year's Eve gatherings.

Police issues a stark warning to short-term Property rental owners after homes were damaged and people inured in a spate of Sydney incidents including gate crashers armed with knives and partygoers bottled, leaving bloody scenes.

Many online short-term rental or homestay booking websites have banned the use of properties for parties, including Airbnb banning certain users if they've not had positive reviews.

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Police said they've been called to numerous large and out of hand events at these types of rentals.

"Police are concerned about the increasing number of public disorder incidents, where homes are being seriously damaged, and the safety of attendees and the broader community is being threatened," Nsw Police Corporate Sponsor for Alcohol-related Crime, Assistant Commissioner Peter Thurtell said.

"Anyone who would be disrespectful enough to trash another person's property would obviously not care about a corporation-imposed party ban, so the onus for protecting the property lies mostly with the owner," he said.

Police used several examples to warn users, including a brawl broken up by the riot squad at a short-stay rental in Schofields on November 20.

More than 20 people were inside and "every room in the four-bedroom property sustained damage".

"Multiple holes in the walls, broken windows and furniture, damage to kitchen appliances and a broken fence," NSW Police said.

"Further, numerous items were reportedly stolen from the home."

Police were also called to a house party at Wentworth Point where over 25 people, including 16 gate crashes, were found armed with knives, hammers and sticks.

"An 18-year-old girl was reportedly hit in the head with a bottle and cut her feet on broken glass," NSW Police said.

"It is also believed personal items were stolen during the incident.

"The two-bedroom apartment sustained significant cosmetic damage and further damage was sustained in common areas of the building."

More than 100 people were found inside a Pyrmont apartment, with police allegedly bottled from the balcony when they arrived.

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Assistant Commissioner Thurtell said if police would not hesitate to take action if they find anyone at these properties committing any kind of criminal activity.

"Violent behaviour will not be tolerated, and we remind people to act sensibly and respectfully. If you are breaking the law, you will be arrested," he said.

Police are urging people to contact local authorities over any concern about a gathering in the neighbourhood.