A gunman armed with multiple weapons went on a shooting spree in a mosque in a suburb of the Norwegian capital Oslo on Saturday, injuring one worshiper before being arrested, police and witnesses said.
The head of the mosque described the assailant as white and said he was wearing a helmet and a uniform.
"One person is shot. The severity of that person's injuries is unknown. One suspect is arrested. The police are working at the location," Oslo police said on Twitter.
The shooting oocurred at the al-Noor Islamic centre in the town of Baerum, an Oslo suburb.
Police said there was no indication that more people were involved.
They said they had no information about the suspect, other than he was described as "white". 
"One of our members has been shot by a white man with a helmet and uniform," Irfan Mushtaq, head of the mosque, told local newspaper Budstikka.
He later told broadcaster TV2 that the man had carried multiple weapons.
"An ethnically Norwegian man with a shotgun and pistols entered the mosque and broke glass windows. He started shooting around him," Mushtaq said.
Public broadcaster NRK reported that police had found multiple weapons inside the mosque, and that someone in the building had managed to subdue the suspect before police arrived on the scene.
The Norwegian Police Security Service (PST) said it was monitoring the situation.
"We're following the events and are continuingly evaluating. It's to early to draw any conclusions," Martin Bernsen, information director at PST, told NRK.
There has been recent spate of white nationalist attacks in the West, including in the United States and in New Zealand where 51 Muslim worshippers were killed in March in shootings at two mosques in the city of Christchurch.
The suspect in the Christchurch killings wrote a hate-filled manifesto in which he said he was influenced by far-right ideologues including Norwegian mass murderer Anders Behring Breivik.
Breivik, who said he was motivated by his hatred of multiculturalism, killed 77 people in gun and bomb attacks in Norway in July 2011, many of them teenagers.