There has been a surge in Maoist violence in recent months
One of India's top Maoist leaders, Venkateswar Reddy alias Telegu Deepak, has been arrested in Calcutta, police have told the BBC.
They said that that Mr Deepak was arrested on the outskirts of the city late on Tuesday.
Mr Deepak is known to be a close associate of Maoist military wing head Koteswara Rao and is believed to have masterminded numerous attacks.
He is the latest of several senior Maoists to be arrested.
In September another senior Maoist, Kobad Ghandy, was arrested in Delhi.
In October police also arrested a husband and wife - who they said were senior Maoist leaders - in the state of Jharkhand.
Police say that Mr Deepak planned last month's attack on a camp of the Eastern Frontier Rifles, in which 24 paramilitary soldiers died.
They say that he was a member of the Central Military Commission of the Communist Party of India (Maoist).
The BBC's Subir Bhaumik in Calcutta says that he is easily one of the biggest catches in the ongoing anti-Maoist offensive in several states called Operation Green Hunt.
Our correspondent says that the arrest comes against the backdrop of the apparent failure to get negotiations started between the Indian government and Maoist rebels after both sides put forward their conditions for talks.
More than 6,000 people have died during the rebels' 20-year fight for communist rule in many Indian states.
Prime minister Manmohan Singh has described the Maoist insurgency as India's "greatest internal security challenge".
The rebels now have a presence in 223 of India's 600-odd districts.