The Shiveluch volcano on the Kamchatka Peninsula in the Russian Far East has become extremely active, threatening a powerful eruption, the Kamchatka Volcanic Eruption Response Team said on Sunday.
"A growth of the lava dome continues, a strong fumaroles activity, an incandescence of the lava dome, explosions, and hot avalanches accompanies this process," the observatory said on its website.
"Ash explosions up to 10-15 kilometers (9.32 miles) ... could occur at any time. Ongoing activity could affect international and low-flying aircraft."
Russia's state RIA news agency cited Alexei Ozerov, the director of the Institute of Volcanology and Seismology of the Far East Branch of the Russian Academy of Sciences, as saying that the dome of the volcano is very hot.
"At night, the dome glows almost over its entire surface. Hot avalanches with a temperature of 1000 degrees Celsius (1,832F) roll down the slopes, pyroclastic flows descend. This state of the dome is observed, as a rule, before a powerful paroxysmal eruption."
Shiveluch, one of Kamchatka's largest volcanoes with a summit reaching 3,283 meters (10,771 feet) is also one of the peninsula's most active ones, with an estimated 60 substantial eruptions in the past 10,000 years.
The volcano last most powerful eruption took place in 2007, according to NASA.