Alexei Ozerov said Mount Karymsky, which is 1,500 meters (about 4,900 feet) high and is located in the southeast of the Kamchatka Peninsula on the Pacific, had thrown up ash to a height of 1,500 meters Wednesday.
According to an observatory in Alaska, a 15-kilometer ash train stretches from the volcano eastwards at a height of 4,000 meters.
Ozerov said Mt. Karymsky's activity was normal for the period of the current eruption, which began in 1995.
Although the volcano poses no threat to local settlements, its ash may prove to be poisonous if breathed in.