The Institute of Volcanology and Seismology of the Far Eastern Branch of the Russian Academy of Sciences has declared "red," the highest danger level, for aviation, according to TASS news agency.

There was a threat that streams of hot lava could block the road, the institute warned.

The institute also noted the volcano ash could travel up to 20 km and block the Petropavlovsk-Kamchatsky-Ust-Kamchatsk highway.

The sky was covered with a black cloud within a radius of several tens of kilometers from the volcano, with thunder rumbling due to static electricity in the ash cloud.

Ashes began to fall in the village of Klyuchi in the Ust-Kamchatsky District of the Kamchatka Territory, where about 4,000 people live.

The thickness of volcanic ash in Klyuchi village has reached 8.5 cm. Due to the eruption, some schools are closed on Tuesday.

Shiveluch is one of Kamchatka's largest volcanoes, with a height of more than 3,200 meters. It includes three main structures: the Old Shiveluch volcano, an ancient caldera and the active Young Shiveluch volcano.