It appears that a major eruption is underway at the Shiveluch volcano in the Kamchatka peninsula. Here is the location from Google Earth:
Here is a recent photo (August 27th) showing it building a lava dome in the crater. There is speculation on some blogs that the dome has collapsed and has been blown out.
Here is part of the KVERT release:
Strong explosive eruption of Sheveluch volcano with ash explosions >10 km (>32,800 ft) ASL probably continues. The activity of the volcano could affect international and low-flying aircraft.
From the excellent Volcansim Blog
Reports from Russia indicate that a large eruption of Shiveluch began yesterday. A bulletin from the Kamchatka Volcanoes Emergency Response Team (KVERT), issued at 22:35 UTC on 10 September warns that ‘Ash explosions > 10 km (>32,800 ft) ASL from the volcano could affect international and low-flying aircraft’. According to the bulletin, ’strong explosions’ occurred between around 14:19 and 14:55 UTC on 10 September, with seismic data indicating ash plumes reaching 15000 metres above sea level; if ash plumes are indeed reaching 10-15 km altitude, then this is a sizeable event. The bulletin reports that according to seismic data ‘10 volcanic events (ash explosions and hot avalanches or pyroclastic flows) occurred at the lava dome from 16:33 till 20:25 UTC on September 10′. Whether the activity is still continuing is not clear, and there are no visual or satellite images of this event because of cloud cover.
Tokyo VAAC issued a volcanic ash advisory at 04:40 UTC today reporting emissions at FL210 (21000 feet / 6400 metres) at 02:16 UTC, but giving no subsequent eruption cloud observations. No further advisories have been issued, so perhaps things have calmed down again at Shiveluch.
The Russian press gives no additional information on this eruption, but reports that KVERT volcanologists have said that there is no danger to local inhabitants from this burst of activity.
KVERT: information releases – current activity summary for Kamchatka volcanoes
Kamchatkan Volcanic Eruption Response Team – KVERT information page from the AVO