MM Praharaj, a senior police official, said the attackers were planning to steal large quantities of explosives used for mining, but fled without them when more police reached the area.

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Praharaj said the fighters were probably trying to disrupt the upcoming national election, due to start on Thursday.

"We are trying our best to ensure that the polls are conducted peacefully,'' he said.

The Maoists, who say they are fighting for the rights of poor farmers and landless labourers, have threatened to chop off the hands of voters if they go to polling booths.

Nalco is one of India's largest aluminium exporters and the Panchpatmali mines are the company's main sources of bauxite, the primary ingredient in aluminium.

The company said the open pit mine, with a deposit of more than 310 million tonnes of bauxite reserves, would be closed for at least a day as a result of the attack.