STOCKHOLM — Swedish police in the southwestern city of Gothenburg have arrested four people suspected of preparing a terror attack, Swedish media said Sunday quoting intelligence reports.

"Four people suspected of preparing a terror attack" were arrested late Saturday, said TT news agency quoting Sara Kvarnstroem, spokesman of the Saepo intelligence agency.

The arrests were announced after hundreds of people were evacuated from Gothenburg's Roeda Sten building, venue of the city's art biennale, on Saturday night.

Contacted by AFP, Saepo would not confirm the report which was also carried by the Expressen tabloid.

"We were warned of a possible threat," biennale official Ulrika Sten told the press.

"Police helped us evacuate the building," she said. "They have started searching the premises and the area has been closed off."

Police did not give details about the four arrested or the circumstances of the arrest.

But TT agency said they were arrested near the biennale building.