STOCKHOLM (Reuters) - Sweden's National Security Service (SAPO) said on Sunday it had arrested four people on suspicion of planning a terror attack on Gothenburg, the country's second-largest city.
Ulf Edberg, spokesman for the Vastra Gotaland police in west Sweden, said a culture and arts arena had been cordoned off after information was received about a potential threat.
"We decided to clear the area because of a threat that could have involved serious danger to life, health or extensive destruction of property," Edberg said.
The area was reopened at 0400 GMT (12 a.m. ET) on Sunday, the tenth anniversary of the Sept 11 attacks in the United States.
"Four people were arrested on suspicion of the preparation of terrorist acts," said Sara Kvarnstrom, press secretary at SAPO.
The arrests were made on Saturday with assistance from the police counter-terrorism unit, she said.
Violence, or the threat of it, has risen in the Nordic region in recent years. A botched bomb attack took place in the Swedish capital Stockholm last December, killing only the bomber.
Norwegian mass killer Anders Behring Breivik admitted to killing 77 people on July 22 -- eight in a bombing in Oslo that badly damaged the Norwegian government quarter, and 69 gunned down on a nearby island.
(Reporting by Mia Shanley; Editing by Matthew Jones)