BUDAPEST - Hungary does not need financial help, but welcomes expertise to help contain a deadly toxic mud spill that has devastated villages and is threatening its waterways, Prime Minister Viktor Orban said Thursday.

"Hungary is strong enough to be able to combat the effects of such a catastrophe on its own. So, we don't need financial help from abroad," Orban said during a visit to the village of Kolontar in the west of Hungary, which was among the hardest hit by the accident.

"But we're still open to any expertise which will help us combat the pollution effects," he added in a news conference broadcast on public television.

Four people died in Kolondar on Monday after the containing walls of a residue reservoir at an alumina plant burst, sending 1.1 million cubic metres (38.8 million cubic feet) of toxic red sludge into surrounding villages, leading the government to call a state of emergency in the affected areas.

More than 120 people were injured, suffering burns, and three people are still missing.

The mud - a residue from aluminium production which is highly corrosive and contains toxic heavy metals such as lead, cadmium, arsenic and chromium - destroyed all vegetation other than trees and seeped into hundreds of houses in villages.

Witnesses say the force of the wave was so strong that cars were sucked out from their garages and it tore out windows and doors, covering everything.

A bridge in Kolontar was swept away and the army had to build a temporary one to replace it.

Orban suggested reconstruction of Kolontar could be very problematic.

"Unfortunately, my impression is that any reconstruction, beyond the bridge, would be useless," he said.

"It'll probably be necessary to clear a new area for the villages and pull down the destroyed part for good. It'll be impossible for people to live here," Orban said.