Honolulu: A fast-moving lava flow from Hawaii's Kilauea volcano led officials to close a highway and to warn that sharp, thin strands of volcanic glass fibres carried on the wind could injure eyes and lungs.

Hawaii County's civil defence agency said lava was quickly approaching Highway 132, prompting the closure from Lava Tree State Park to Four Corners, and warned residents to monitor their radios and phones for updates and evacuation orders.

Earlier on Tuesday, a small explosion of ash erupted from the summit of the volcano in a vertical plume about 4600 metres high, the US Geological Survey said, the latest outburst in a month of volcanic activity.

The agency warned that ash was drifting north-west and was liable to affect anyone in the summit area. Hundreds of people have been ordered to leave the vicinity of one of the world's most active volcanoes.

Kilauea entered its fourth week of what may be an unprecedented, simultaneous eruption at its summit crater and along a 10-kilometre string of fissures 40 kilometres down its east flank.