A 10-year-old Norwegian boy who took his parents' car for a joyride last week, claiming he was a dwarf who forgot his driver's license, has hit the road again.

This time he took off in the car of a relative the family was visiting and managed to drive about 30 km (19 miles) before stopping, local police said.

When the parents realized what happened, they phoned police who sent out messages over Twitter and traffic radio asking the public for help. The boy eventually stopped and a bystander took his keys away, police said.

The boy caused a stir last week in Dokka, his hometown about 110 km north of Oslo, when he loaded his 18-month-old sister in the family car and drove off to visit their grandparents 60 km away, only to drive into a snowy ditch after 10 km.

Police had considered the case closed. But they were not so forgiving about the second incident and have reported the family to child services.

"Nobody was injured, but that was more due to luck than anything else," Baard Christiansen, a spokesman for the Vest Oppland police, told Reuters. "The adults around the boy must take responsibility now before a tragedy occurs.

"It is scary and very sad that he is allowed to keep going on like this," he said.