Norwegian police said Tuesday they were investigating an explosion near the Israeli embassy in central Oslo, warning the public to stay clear after finding additional undetonated explosives.

No injuries were reported, but officials said the blast was likely caused by a planted hand grenade left on a tramline.

Police arrested a 13-year-old suspect and are probing whether others were involved, though they suggested the attack may be linked to criminal disputes.

The site is close to a university campus, the royal palace, and the Israeli embassy, the Jerusalem Post has reported.

The incident came a day after drone sightings forced temporary airspace closures at Oslo and Copenhagen airports.