Northern Territory Police have arrested an 18-year-old man after a St John Ambulance vehicle was damaged in Malak early this morning.

About 3.30am, paramedics were called to a residence following reports of a medical episode.

As the ambulance stopped near the residence, the man allegedly approached the vehicle and struck its windscreen with a length of chain, causing extensive damage.

The paramedics immediately drove from the area to a safe location and police were called.

Police, including members of the Dog Operations Unit, responded and established a cordon around the area.

A police dog team tracked the alleged offender, who was located nearby and arrested.

Police are also investigating reports the man assaulted his mother at the residence before the ambulance arrived.

Investigations are continuing.

Anyone who may have information relating to the incident are urged to contact NT Police on 131 444 or you can report anonymously to Crime Stoppers on 1800 333 000. Please quote reference number P26310194.