Suspected Maoist rebels have killed at least 10 Indian policemen in a landmine attack in the eastern state of Orissa, officials say.
Another 10 policemen were injured in the explosion, which ripped apart the bus in which they were travelling.
The blast came as India's home minister reiterated an appeal to the rebels to abandon violence and hold peace talks.
The rebels are fighting in rural areas to establish communist rule in a large swathe of India.
More than 6,000 people have died in the 20-year fight.
The Maoists say they are fighting for the rights of the rural poor who they say have been neglected by governments for decades.
Sunday's blast occurred in Koraput district, about 525 km (235 miles) south-west of the state capital, Bhubaneshwar.
"We are confirming 10 deaths, but it may go up," senior police official Sanjeev Panda told reporters.
He said a search for more bodies was under way.
The authorities recently began a major operation against the rebels in a number of states.
Nearly 50,000 federal paramilitary troops and an equal number of policemen, equipped with helicopters and unmanned aerial surveillance vehicles, are taking part.
In West Bengal state neighbouring Orissa, Home Minister P Chidambaram visited the former rebel stronghold of Lalgarh and reviewed the progress of the offensive.
He said the rebels had been weakened and called them "cowards".
"Why are they hiding in forests? We have invited them for talks after they abjure violence," Mr Chidambaram told reporters.
"If they really want development, if they really want to discuss problems of the people, they are welcome to talk."