A number of policemen are feared dead after Maoist rebels attacked a security convoy in central India, police say.
Police said 12 of the 40 policemen in the convoy had not returned to their bases after the incident.
The attack happened in the rebel stronghold area of Dantewada, in Chhattisgarh state.
Thousands of people have died in the course of a 30-year insurgency being fought by the Maoists across a swathe of central and southern India.
The rebels say that they are fighting for the rights of landless farmers and neglected tribes.
State police chief Vish Ranjan said that some of the "missing" policemen could have been killed in the attack.
Six of the 28 policemen who did return to their bases after the attack had sustained injuries, he said.
The rebels have a strong presence in eight of 16 districts of Chhattisgarh state.
Last month, at least 24 soldiers and police and 20 Maoists were killed in clashes in the state of Chhattisgarh.
In March, 55 policemen were killed in an attack on a security post, the worst Maoist assault in Chhattisgarh.
More than 6,000 people have died during the rebels' decades-long fight for a communist state in parts of India.
Prime Minister Manmohan Singh says the Maoists pose the most serious threat to national security in India.
The rebels operate in 182 districts in India, mainly in the states of Jharkhand, Bihar, Andhra Pradesh, Chhattisgarh, Madhya Pradesh, Maharashtra and West Bengal.