OSLO: Norwegian police said they arrested an armed man who stole an ambulance in Oslo on Tuesday then ran down and slightly injured four pedestrians, including twin babies.

Police said they were searching for a second suspect - a woman described as having fair skin, brown hair and wearing a black jacket, around 1.65 metres (5 feet 4 inches) tall and “who appears to be under the influence”.

“We have no information for now indicating that this is terror-related,” Oslo police wrote on Twitter.

According to the TV2 channel, the arrested man is in his 30s and the woman being sought is in her 20s. Both are Norwegian nationals and known previously to the police.

Earlier, police said they had “taken control of an ambulance that was stolen by an armed man”. Police officers had fired shots to arrest the suspect, who was not seriously injured.

“A woman with a pram and an elderly couple were run over or had to throw themselves out of the way” of the stolen vehicle, police said in another Twitter post, adding that the woman and a child were taken to hospital.

Oslo University Hospital said seven-month-old twins were involved in the incident, one of whom was lightly injured while the status of the other was not yet determined.

Television images showed a damaged pram lying by the roadside, and an upturned traffic sign.

Attacks by rightwing extremists

Witnesses cited by public broadcaster NRK said police shot at the tyres of the ambulance and the driver fired back, which police have not confirmed. Pursued by police, the ambulance then crashed into a gate outside a residential building.

Television images showed a heavily damaged Mercedes ambulance with what appeared to be several bullet holes in the front left door.

According to media reports, the armed man hijacked the ambulance after the vehicle he and the woman were in overturned in an accident.

Police said they had seized two weapons at the scene.

The incident took place in a residential neighbourhood in northern Oslo. Students at a nearby school and daycare centre were ordered to remain indoors.

A large number of police officers, some of them heavily armed, were deployed at the scene, and a helicopter hovered overhead for a while.

The suspect’s motive was not immediately known, police said.

Norway has experienced several terrorist attacks by rightwing extremists, including the July 2011 twin attacks by Anders Behring Breivik that left 77 people dead.

There have however been no attacks carried out by Islamist extremists on Norwegian soil.