Three males, aged 13, 15 and 20-years-old, have been arrested after assaulting workers in a carpark of a shopping centre in Casuarina.

About 8:25pm last night, police received reports of four cleaners being assaulted by three males in separate incidents. It is alleged the first three cleaners were physically assaulted and the fourth cleaner was threatened with a hammer while the group demanded money and jewellery. No injuries were reported.

Casuarina General Duties and the Dog Operations Unit deployed and arrested the three males nearby.

The 13-year-old male will be dealt with under the provisions of the Youth Justice Act.

The 15-year-old male was charged with Assault with Intent to Steal and is awaiting bail review.

The 20-year-old male was charged with Assault with Intent to Steal and was remanded to appear in the Darwin Local Court later today.

Casuarina General Duties Officers have carriage of the investigation.

Anyone who witnesses or experiences crime or anti-social behaviour is urged to contact police on 131 444. In an emergency dial Triple Zero.