Northern Territory Police have charged a woman after a police vehicle was set alight during unrest in Alice Springs on Thursday night.

About 9:30pm, a large group gathered at Alice Springs Hospital, where disorderly and riotous behaviour occurred.

It is alleged that about 10:40pm, the woman used a lighter and dried grass to start a fire beneath a Southern Traffic Operations vehicle.

Police observed the incident and moved in immediately, arresting the woman at the scene. The fire was quickly extinguished before it could spread further.

Despite this, the vehicle sustained about $20,000 damage as the unrest continued.

The woman has been charged with one count of attempt arson and one count of taking part in a riot.

She remains in custody and is expected to face court next week.

Investigations into the incident are ongoing.