Security forces seized 543 anti-personnel mines as well as ammunition in Kolkata on Thursday, busting a smuggling racket from a state-run ammunition factory, a defence spokesman said.
Three people, including a soldier, were arrested, Wing Commander Ramesh Kumar Das told a news conference.
"This is one of the largest recoveries of arms smuggled out of a ammunition factory and these could be for Maoist rebels as they use them these days," Das told reporters.
"The anti-personnel mines are very powerful and a single mine can kill many," he said, adding that a joint army intelligence and police team had found the huge stash of arms including more than 1,000 bullets in a house in a southern suburb of the city.
Maoist rebels, who claim to fight for India's 'poor peasants' and 'landless labourers', operate across eastern, central and southern states and often use mines to attack police convoys.
Das said more people could be arrested including employees working in the Kolkata arms unit, one of India's biggest munitions factories.
Thousands of people, including hundreds of policemen, have been killed in Maoist violence in the past decade in the country.