Stig Millehaugen, 53, was sentenced in 2012 for his refusal to 21 years in prison for the murder of a gang leader.

He has served his sentence at the institution in Trondheim.

In 1993, he was convicted of the murder of a prison guard in connection with another escape.

Since Wednesday, he is at large when he escaped from a short leave he had had during the day.

According to information to NRK, he should instead have boarded the flight to Oslo.

Surveillance videos released by the police show how Millehaugen moves at Trondheim airport with a backpack.

The theory: Can be in Sweden

GP experiences that the police during the night until Friday carried out an operation in northern Bohuslän in search of the double killer.

One of the police's theories is that he may be in Sweden.

- We are open because he can be somewhere other than in Norway, it has been so long now.

He is internationally wanted and we have contact with the Swedish police just as with other police.

It is one of several possibilities that he is in Sweden, says police inspector Trude Buanes to GP.