Norway Police Investigate Explosion Near Israeli Embassy

Norwegian police said on Tuesday they were investigating a blast near the Israeli embassy in central Oslo and warned people to stay away from the location as there were likely more explosives present.

There were no report of injuries at the site, located in the immediate vicinity of a university campus and some 500 meters (yards) from the royal palace and the Israeli embassy.

Incident commander Brian Skotnes confirmed to Aftenposten that one person was arrested, but police were investigating the possibility that other people were involved.

Police officials told local media that they believed the explosion was caused by a planted hand grenade, and undetonated explosives were discovered on site. The grenade was reportedly left on a tramline.

The explosion comes a day after Reuters reported airports in Oslo and Copenhagen closed due to drone sightings.

Oslo Airport shut its airspace from midnight local time (2200 GMT) due to a drone observation, a spokesperson for Norwegian airport operator Avinor said in an emailed statement, adding that all flights were diverted to the nearest airport.

The second device found at the site appeared to be a "military-style" hand grenade, the police officer in charge at the scene, Brian Skotnes, told reporters.

"We've apprehended one suspect and are intensively seeking more information as well as other people," Skotnes said.

"Our hypothesis is that it is criminals who have an agenda against other criminals, but we cannot rule out anything."

The area was now safe, he added.

A 13-year-old was apprehended by police, TV2 and daily Aftenposten reported, citing unnamed sources.

Residents warned of explosion

In a rare step, authorities sent an emergency message to Oslo residents' mobile phones, warning them about the blast.

"There has been an explosion in the area (called) Pilestredet. Given that there is still an explosive device in the area, the police wish that people stay away from windows," the message said.

"As of now, we are not evacuating the area."

The incident comes nearly a day after reports of drone sightings near Oslo's and Copenhagen's airports.