A man has been fined $2,000 after police found a child in a car boot and three more unrestrained children in the back seat of a vehicle in south Canberra.

About 4:45pm yesterday ACT Policing responded to reports of a man driving with children who were not wearing seatbelts on Hindmarsh Drive in Phillip.

Officers issued the driver with five infringement notices for the offences, including three for no seatbelt, one for a non-fastened seatbelt and one for travelling in a part of the car designed for carrying goods.

One of the children not wearing a seatbelt was aged between one and seven, police said.

The man was fined $2,056 and lost 12 demerit points.

Acting officer in charge of traffic operations Paul Hutcheson stressed the importance of seatbelts, especially for children.

"If you don't wear a seatbelt and are involved in a collision, your chance of being seriously injured or even killed significantly increases," he said.

"Always ensure children are restrained correctly, even when travelling at low speeds or on short trips."