CHAITEN, Chile : Ash from the erupting Chaiten volcano in southern Chile spread across a growing swathe of South America on Wednesday, forcing flight cancellations across much of Argentina and threatening to blanket more towns in Argentina and Chile.

The volcano, located 1,300 kilometres south of Santiago near the border with Argentina, erupted violently on Tuesday, raining ash and lava over its surroundings and forcing a total evacuation in a 30-kilometre radius, Chile's National Emergency Office said.

The long-dormant volcano began rumbling and belching smoke on Friday.

The 4,000 residents of Chaiten, the town nearest to the volcano, were evacuated on Tuesday, and only a handful of emergency personnel and news reporters remained.

The volcano's dense 30 kilometre high plume of ash took a northeasterly turn overnight Tuesday to Wednesday after moving for days in a southeasterly direction, Office of National Emergencies head Rodrigo Rojas told AFP.

Ash from the volcano is expected to blanket the Chilean town of Palena and the Argentine ski resort Bariloche northeast of Chaiten, according to Rojas.

Otherwise "there have been no reports of significant changes in seismic activity or emission of ashes" since the volcano began to erupt violently on Tuesday, Rojas said.

Flights were cancelled from Buenos Aires to most of the major southern Argentine cities due to ash from the Chaiten eruption.

Three leading airlines - Aerolinas Argentinas, Austral and Chile's LAN - cancelled flights across the region, including flights to the Atlantic port cities of Bahia Blanca - 900 kilometres northeast of the volcano - and Comodoro Rivadavia, located 575 kilometres southeast of the volcano.

"The airports are open but the airlines cancelled flights because the volcanic ash gets in the airplane turbines and could cause material damage," said an aviation official at the Jorge Newbery airport north of Buenos Aires.

The airport source said it was likely that flights would remain grounded Thursday given the weather forecast.

Officials in the Argentine province of Chubut east of the eruption said some 160 schools closed since Friday due to the volcanic ash reopened on Wednesday.

A Chilean vulcanologist warned on Tuesday that the eruption was only at the beginning stage, and that an explosive eruption was possible.

"There could be a major explosion that could collapse the volcano's cone," said Luis Lara of the National Geologic and Mining Service. - AFP/de