Indian police on Monday killed at least 21 rebels in a shoot-out in eastern India, a local officer said, one of the deadliest incidents this year in a long-running Maoist insurgency.

Police said they ambushed a meeting of 30 to 40 Maoists in a forest near the border of Odisha and Andhra Pradesh states, triggering a gunbattle.

"Now 21 bodies of the Maoists have been recovered. The search operation is still on," sub-inspector C.K. Dharua told AFP by telephone from Malkangiri district in Odisha where the attack occurred.

Dharua had earlier confirmed 18 deaths but warned the toll could rise as "there was a large number of people at the meeting".

A top Maoist leader and his son were suspected to be among those killed, the Press Trust of India news agency said, citing unnamed police. 

Local media also said two police officers were injured in the battle, but that could not immediately be confirmed.

Dharua said weapons including four AK-47s and three self-loading rifles were recovered from the rebels in the forest, some 640 kilometres (400 miles) from the state capital Bhubaneswar.

India's Maoist insurgency began in the 1960s, inspired by Chinese revolutionary leader Mao Zedong, and has cost thousands of lives.

The rebels, described by former prime minister Manmohan Singh as India's most serious internal security threat, say they are fighting authorities for land, jobs and other rights for poor tribal groups.

Monday's gunbattle comes after 10 paramilitary commandos in eastern Bihar state were killed in July after suspected Maoist rebels ambushed their convoy and set off a series of homemade bombs.

In March, suspected rebels triggered a powerful landmine blast in central Chhattisgarh, killing seven policemen.

The rebels operate in at least 20 Indian states but are most active in the forested and resource-rich areas of Chhattisgarh, Odisha, Bihar, Jharkhand and Maharashtra.

They draw recruits from tribal communities whose members are often desperately poor and living in underdeveloped areas neglected by successive governments.

The Maoist insurgency has claimed more than 7,000 lives between 2005 and 2016, according to the South Asia Terrorism Portal website which tracks separatist trends.

The remote forests of Malkangiri district are a major transit point for rebels because it borders Maoist-strongholds in Chhattisgarh and Andhra Pradesh, the Hindu newspaper said Monday.

Prime Minister Narendra Modi has been seeking to stem the insurgency by earmarking development funds for revolt-hit areas and improving policing.

Last year, Modi urged Maoists to put down their guns and take up ploughs, saying "violence has no future".

Government critics say attempts to end the revolt through tough security offensives are doomed to fail, and the real solution is better governance and development of the region.

Source: AFP