The Northern Territory Police Force are investigating after an aggravated assault at the Royal Darwin Show this evening.

Around 8:20pm, police received reports that a 15-year-old male had assaulted another 15-year-old male with a knife at the showgrounds after an altercation.

Police and St John Ambulance attended, and the victim was conveyed to Royal Darwin Hospital in a serious condition.

The offender fled the scene, and efforts are underway to locate him.

A crime scene has been declared and police are urging anyone with information to make contact on 131 444 and quote reference P25199834.