One of Russia’s most active volcanoes has erupted, sending a five-kilometer-high cloud of ash into the sky over the eastern Kamchatka Peninsula. A “Code Red” warning was briefly issued for aircraft.

According to volcanologists from the Russian Academy of Sciences, the Shivelukh volcano began erupting shortly after a strong 7.0 magnitude earthquake struck off the east coast of Kamchatka over the weekend.

They warned that another, even more violent earthquake could be imminent.

The Academy’s Institute of Volcanology and Seismology released a video showing the ash cloud over Shiveluch, which stretched for 490 km east and southeast of the volcano.

The Ebeko volcano on the Kuril Islands also emitted ash 2.5 kilometers high, the institute said. It was not explicitly stated whether the eruptions were triggered by the earthquake.

A Code Red ash cloud warning briefly put all aircraft in the region on alert, the Kamchatka Volcanic Eruption Response Team reported.

A separate report by the official Tass news agency said there were no disruptions to commercial air traffic and no damage to aviation infrastructure.

Is another earthquake on the way?

The tremors in the region could be the prelude to an even stronger earthquake in southeastern Kamchatka, Russian scientists warned.

The Institute of Volcanology said a possible second quake could occur “within 24 hours,” with a magnitude of nearly 9.0.

There were no immediate reports of injuries from the weekend’s earthquake, according to Russian emergency officials. The quake struck six kilometers below the seabed and its epicenter was 108 kilometers southeast of the nearest city.

Russian news agencies reported the strongest earthquakes “in a long time,” citing residents of Petropavlovsk-Kamchatsky, a port city of more than 181,000 people located across from a bay with a major Russian submarine base.