(CNN)Police are guarding Jewish centers across the Swedish city of Gothenberg following an arson attack on a synagogue there, police said.
Three men, all in their twenties, have been detained for questioning in relation to the Saturday night incident, police said.
Spokeswoman Ulla Brehm said that police received reports shortly after 10 p.m. local time that burning objects had been thrown into the yard of the synagogue, causing a fire. Brehm said approximately 10 people dressed in black were seen running away after throwing the objects.
No one was injured in the attack and the projectiles thrown did not make it inside the synagogue. Police are not describing the objects as Molotov cocktails.

Authorities used surveillance camera footage to identify the three men who are being questioned. The police are not reporting their nationalities.
A number of people were attending an event at the adjacent Jewish community center when the attack happened. Nobody at the community center was hurt and all the event participants were escorted safely off the premises.
Gothenburg is in southwestern Sweden, about 230 kilometers (143 miles) north of Copenhagen.