(CNN)At least 22 members of Indian security forces were killed and 31 injured on Sunday during a four-hour gun battle with Maoist insurgents, officials said.
Security forces in the central state of Chhattisgarh were conducting an operation against the left-wing insurgent group, in the state's Bastar Division, when one of the teams came under attack from the insurgents, chief of Chhattisgarh police DM Awasthi said on Sunday.
They were carrying out a mission to set up camp in an area "considered the stronghold" of Maoist insurgents, which "agitated them," said Bhupesh Baghel, chief minister of Chattisgarh, on Sunday.
The ensuing battle included "bullets, grenades and rocket launchers" from both sides, he added.
Search operations for a missing security member are still underway.
"We have received information that he is alive and is somewhere in the depths of the jungle, our rescue operation is ongoing," said Sundar Raj P, Inspector General of Police in Bastar, on Tuesday.
He added that they suspected that the missing official was abducted when they couldn't find his body or any signs that he had died.
The government has been embroiled in a decades-long conflict with Maoist rebel groups, also known as Naxals, who launch attacks on government forces in an attempt to overthrow the state and usher in a classless society. Maoists are largely active in central India, in regions mainly populated by tribal peoples.
Militant attacks in several states, including Maharashtra, Odisha and Chhattisgarh, where the rebel movement still has traction, are common.
Bastar Division, where Sunday's battle took place, includes the Sukma-Bijapur border areas -- an area thought to be among a number of key Maoist strongholds.
India's Prime Minister Narendra Modi expressed his condolences on Sunday in a tweet saying, "My thoughts are with the families of those martyred while fighting Maoists in Chhattisgarh. The sacrifices of the brave martyrs will never be forgotten. May the injured recover at the earliest."
Naxalite groups have been active in the country since the 1960s, but the modern insurgency did not begin until the early 2000s. Former Indian Prime Minister Manmohan Singh once described Maoist rebels -- who are well organized and trained -- as the country's "gravest internal security threat."
More than 2,100 civilians in India have been killed in the Maoist insurgency since 2010.
In April 2017, 25 police officers were killed and six others injured when hundreds of suspected Maoist rebels attacked a convoy in central India.
Suspected Maoists also struck during India's elections in 2019, allegedly gunning down a polling supervisor in the eastern state of Odisha. In another incident in the same district that year, alleged Maoists approached a vehicle heading towards a polling center and forced officials to disembark before setting fire to it.
According to a 2019 report by India's Ministry of Home Affairs, 90 districts across 11 states are affected by some form of Naxal or Maoist militancy.
The government has responded to the Maoist insurgency with a security crackdown in areas in which the groups are active, an approach that while appearing to reduce the threat level has been criticized by some observers as heavy-handed and prone to abuse.
The villagers who live in Maoist territory are largely cut off from the country's rapidly growing economy, and many live in fear of rebels taking their children as recruits, or of violent government raids. In 2017, villagers in Chhattisgarh told CNN that they were forced to pay taxes to the Maoists, or face abuse or even torture. But if they did pay up, they risked being labeled Maoist sympathizers by government forces.