Norwegian Justice Minister Tor Mikkel Wara is to leave his post temporarily after his partner was arrested on suspicion of setting fire to his car.
Laila Anita Bertheussen, 54, was detained by Norway’s PST security agency in the wake of five incidents at the minister’s home.
She is currently suspected only in the 10 March arson attack but will also be investigated over the other attacks.
Prime Minister Erna Solberg said it was a tragedy for Mr Wara and his family.
“This information came as a shock to me and to the entire government,” Ms Solberg told a dramatic news conference in Norway.
The prime minister was told about the arrest about an hour before police made the details public.