Explosions intensify on Hawaii's Kilauea volcano, spewing ash and sparking a red alert for aviation for the first time since the latest eruption began 12 days ago.

The Kilauea volcano, the most active in Hawaii, is highly unstable as lava spouts into the air and fissures emit deadly gases -- hazards that have forced thousands of people to evacuate.

A series of fresh earthquakes, including a powerful magnitude 6.9, hit Hawaii's Big Island, where the Kilauea volcano has been spewing fountains of lava into residential areas and forcing hundreds to evacuate.

The US state of Hawaii's Kilauea volcano erupted Thursday, causing lava to spew out of ground fissures in residential areas and prompting thousands of people to flee.