On Monday, the Shiveluch volcano erupted, belching out ash plumes to altitudes of 6 to 11 kilometers in three distinct bursts.
"An explosive-extrusive eruption of the volcano continues. Ash explosions up to 12 km ... [above the sea level] could occur at any time. Ongoing activity could affect international and low-flying aircraft," the statement read.
The eruption occurred at 2:51 p.m. local time (03:51 GMT), the scientists said. A red hazard code has been issued for aviation, indicating a threat to local and international air traffic.
The Shiveluch volcano is located 50 kilometers north of the village of Klyuchi and about 450 kilometers from the city of Petropavlovsk-Kamchatsky.