Maoist rebels killed 22 Indian security forces and injured 30 others in a central Indian state, police said Sunday, making it the deadliest ambush of its kind in four years.

The forces were ambushed Saturday while returning from a search operation near a forest in Bijapur district in Chhattisgarh, a Maoist rebel stronghold, the state police's additional director-general Ashok Juneja told Agence France-Presse (AFP).

"So far it is confirmed that 22 security personnel were killed," Juneja said. "The search operation is still underway and the exact figure will be known ... late Sunday evening."

The injured personnel were admitted to two government-run hospitals in Bijapur and Chhattisgarh's capital city Raipur. More than a dozen others remained missing, he said, adding that an unknown number of Maoists were also killed in the encounter.

Juneja said the rebels looted weapons, ammunition, uniforms and shoes from the security forces who were killed.

The death toll could rise further, a senior police officer in Bijapur district told AFP. Prime Minister Narendra Modi tweeted that the "sacrifices of the brave martyrs will never be forgotten", while Home Minister Amit Shah wrote on Twitter that India would "continue our fight against these enemies of peace & progress".

Chhattisgarh Chief Minister Bhupesh Baghel wrote on Facebook Sunday that Shah had assured him of "all the necessary help" from the national government against the militants.

The toll was the worst for Indian security forces battling the far-left guerillas since 2017, when 25 police commandos were killed in a previous attack.