There has been a spike in illegal hunting in the Kosciuszko National Park in south east New South Wales.

The National Parks and Wildlife Service said shooters had targeted deer and horses around popular campsites in the Lower Snowy River area near the Victorian border.

"The staff have been finding the carcases of deer with their heads chopped off, presumably the hunters take them as trophies, and they're also shooting horses," Snowy River area manager Pam O'Brien said.

"It really is the last thing that people want to see is these animals lying around, as well as hearing gun shots."

Ms O'Brien said she was also concerned about recent vandalism and illegal dumping at the Pinch River campground south-west of Numbla Vale.

"They had gone to a lot of trouble and pulled out all the bollards and burnt bollards and made a really big mess, so far anyone coming after them it wasn't a pretty site," she said.

"They had left just household garbage as well as burnt gas bottles, bottles, things like that."

Ms O'Brien said the Parks Service was speaking with police and increasing patrols.

She urged visitors to report any suspicious activity.

"We're presuming people have been hearing them and I suppose what we want to do is encourage people to report this kind of activity," she said.

"All information is confidential and we can act more quickly if we hear straight away when these things happen."