Oslo: Norwegian police have boosted security around the country's mosques following a shooting at the al-Noor Islamic centre on the outskirts of Oslo in what they believe was a thwarted far-right terror attack.

The scene of a shooting inside the al-Noor Islamic centre mosque in Baerum, near Oslo on Saturday. Credit:AP

One person sustained light injuries before people attending the mosque overpowered the gunman.

A man in his 20s was taken into custody after the shooting, Oslo police said. Investigators so far think no one else was involved in Saturday's violence at the mosque, located in the Oslo suburb of Baerum.

When officers went to the shooting suspect's residence, they found the body of his 17-year-old stepsister, police said on Sunday evening. The alleged mosque gunman was being investigated in her death, police said.