The Shiveluch volcano on the Kamchatka Peninsula in the Russian Far East has increased its activity and is now in danger of erupting violently, the Kamchatka Volcanic Eruption Response Team said on Sunday.
"As 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 kilometres (9.32 miles) ... could occur at any time. Ongoing activity could affect international and low-flying aircraft."