A Norwegian neo-Nazi heavy metal musician and convicted killer has been arrested in France over fears he may have been preparing a "major terrorist act".
Intelligence officers arrested 40-year-old Kristian Vikernes at dawn on Tuesday at his home in a village in the central Correze region, along with his French wife Marie Cachet, 25.
Police said Cachet had recently bought five rifles, and Vikernes' violent internet postings were proof he posed a potential threat.
The ministry said Vikernes was "close to the neo-Nazi movement" and could have been preparing a "major terrorist act".
Norwegian mass murderer Anders Behring Breivik had sent him the manifesto he published online just before he started his killing spree on July 22, 2011, said the ministry.
Interior Minister Manuel Valls conceded that they had as yet identified "no target, no plan" but intelligence chiefs had decided it was important "to act before and not afterwards".
Vikernes is known in Norway for having stabbed to death Oeystein Aarseth, a fellow member of his band, Mayhem, in 1993. He was sentenced to 21 years prison, and made his home in France after being released early in 2009.
Vikernes, who also goes by the name "Varg", Norwegian for "wolf", had been under surveillance for several years.
But anti-terrorism authorities in Paris opened a probe into the father-of-three at the beginning of the month after his wife bought weapons - albeit legally as she has a permit.
Officers seized five long-range weapons and ammunition at their home.
Explaining the decision to arrest Vikernes, Valls said: "The DCRI [French domestic intelligence service] considered that messages he had posted on the internet expressed huge violence."
"The purchase of weapons and cartridges by his wife showed that a terrorist plan was possible. To know more, to know what this plan could be... the DCRI considered it was important to arrest and question him."
In a statement on the interior ministry website Valls said Breivik had sent Vikernes his extremist manifesto shortly before killing 77 people in two separate attacks in Oslo.
Breivik was sentenced last August to Norway's maximum sentence of 21 years in prison, for the murder of scores of people - mostly students - in a bomb and shooting attack in Oslo.