The long-dormant Nevado del Huila volcano erupted provoking avalanches and floods that swept away houses and bridges and prompted thousands to evacuate.

"There are 10,000 people in the zone, of which we've already evacuated 3,500," Luz Amanda Pulido, director of the national disaster office, told The Associated Press after flying over the volcano in southwest Colombia.There were no reports of deaths or injuries.

The volcano's eruption at 10:37 pm on Tuesday (0907 IST on Wednesday) was its first on record since Colombia was colonised by the Spanish 500 years ago. A second eruption occurred at 2:57 am (1327 IST) on Wednesday.

Experts were not ruling out more eruptions.

"The seismic activity remains light but permanent, and we can't rule out another bigger event in the next hours or days," said Mario Ballesteros, director of the Government's Institute for Geology and Mining.

The eruption sent an avalanche of rocks down the volcano's sides and into the Paez and Simbola rivers, causing them to flood.

"The bridges were swept away, the highway used by the indigenous in the zone was destroyed for various kilometres and the problem we have now is the lack of a route to deliver goods and medicines to the population," Police Gen Orlando Paez said.

President Alvaro Uribe said, he was returning early from the Caribbean port city of Cartagena to visit communities affected by the eruption. The air force said, it was preparing to send a planeload of humanitarian aid.