The Shiveluch volcano on the Kamchatka peninsula in Russia erupted today, sending a vast ash cloud 1,08,000 sq km wide into the sky.
The eruption caused a red aviation warning from KVERT, which said ongoing activity could affect international and low-flying aircraft.
Some schools were closed, and residents were ordered to stay indoors due to the ash fall, which reached depths of up to 8.5 cm.
Lava flows from the volcano melted snow, and caused a mudflow warning for a nearby highway.
The eruption was one of Kamchatka's largest and most active, with an estimated 60 substantial eruptions in the past 10,000 years.
The smaller part of the volcano, Young Shiveluch, has been reported as extremely active in recent months.
Pictures showed the cloud billowing swiftly over the forests and rivers of the far east and of villages covered in ash.
About 3,00,000 people live on Kamchatka peninsula, which juts into the Pacific Ocean northeast of Japan.
There were no immediate reports of casualties, but the volcano was still erupting 15 hours after the start of the eruption.
The Russian Academy of Sciences' Geophysical Survey said the volcano was set to erupt for at least a year, and the process is gradually continuing.