COPENHAGEN, Denmark (AP) — A man with a firearm was detained Sunday after apparently opening fire in central Oslo, police said. No one has been injured.

Police said on Twitter that the man, in his 20s, was detained behind Oslo's downtown cathedral, adding they have no information that shots were fired at people. However, they were seeking witnesses.

Witnesses called police shortly after 9 a.m. (0800 GMT; 3 a.m. EDT) to alert them to a man walking around downtown Oslo with a weapon and firing with live ammunition. Norwegian media reported that police were deployed throughout the city.

The man apparently shot at buildings and the VG tabloid said at least one shop window had a bullet hole. Police tweeted they had found a shop front "with damage that may stem from shots."

The shooting happened around Stortorvet, a square adjacent to the Oslo Domkirke cathedral.