THE US National Weather Service has warned planes to avoid air space near an erupting Alaska volcano as it spewed ash 30,000ft above sea level.

Winds were blowing ash from Pavlof volcano to the west and south west. Pavlof began erupting, pushing lava out from a vent near its summit, on Wednesday. On Friday, the ash cloud reached 16,000ft.

The eruption has since intensified, sending the ash cloud higher, said Dave Schneider, a geophysicist at Alaska Volcano Observatory. It is not clear how long the eruption will last.

Pavlof, about 625 miles south west of Anchorage, is Alaska's most active volcano and lies along popular international air routes connecting Europe, North America and Asia.

The eruption has had little effect on people on the ground apart from some small avalanches. The closest community, Cold Bay, is 40 miles away.