Alaska's Mount Redoubt volcano erupted anew on Thursday, hurling ash and smoke high into the atmosphere, forcing flight cancellations and prompting new precautions on the ground, authorities said.

At 9:24 am local time (17:24 GMT), the volcano began kicking out fresh debris, now reaching up to nearly 20,000 meters (65,000 feet) above sea level, according to the US National Weather Service.

The Alaska Volcano Observatory described the blast as "a major explosive event."

An hour later observers recorded a second strong eruption.

Located close to Anchorage, Alaska's principle city, the 3,100-meter (10,200-foot) volcano has been erupting repeatedly in recent days.

The blasts forced Alaska Airlines to cancel all flights for the remainder of the day to and from Anchorage international airport, 160 kilometers (100 miles) northeast of the volcano and a vital transport hub for the state.

Officials at Elmendorf Air Force Base in Anchorage also said they were "repositioning aircraft as a precautionary measure" due to a risk of ash damage, moving six military aircraft to an unaffected air bases in Alaska and neighboring Washington state to the south.

The Elmendorf base and airfield remain open, officials said in a statement.

Although no injuries have been reported from the eruptions, ash clouds have prompted concern in nearby towns, with authorities placing the region on "Red Alert," with residents warned to prepare for falling ash.

"We expect these activities to last for weeks," said Interior Secretary Ken Salazar earlier this week in a conference call with reporters.

An oil storage site 32 kilometers (20 miles) is also being monitored. When the volcano last erupted, lava that crashed into the Drift River triggered a flood that reached the oil terminal, which was briefly evacuated.

The last significant blast from Mount Redoubt began in December 1989.

Then, ash from the volcanic cloud clogged the four engines of a KLM airlines Boeing 747 that was flying by. The plane plummeted more than 3,000 meters (10,000 feet) before the pilot managed to restart the engines, land the plane in Anchorage and save all 231 passengers.