Indian security forces raided a Maoist rebel hideout in the forests of Chhattisgarh state Saturday, triggering a firefight resulting in the deaths of five paramilitary troops and one rebel, according to a statement by the state's police.

Senior police officer D.M. Awasthi said hundreds of police and paramilitary soldiers took part in the raid after receiving intelligence that a large number of rebels were gathered in the Bijapur district.

He said at least 12 security personnel were injured in the four-hour firefight, and authorities were working to evacuate the wounded to hospitals.

Awasthi said the body of one female rebel was also recovered. The rebels used automatic weapons and grenades during the gunbattle, according to Hemant Kumar Sahu, a paramilitary officer, who spoke with The Associated Press by phone.

State-run All India Radio tweeted that at least 20 security personnel were missing after the engagement.

The Maoist rebels, inspired by Chinese revolutionary leader Mao Zedong, have been fighting the Indian government for more than four decades, demanding land and jobs for tenant farmers, the poor and indigenous communities.

The government has called the rebels India’s biggest internal security threat.

Last month, a roadside bomb killed at least four Indian policemen and wounded 14 in the Narayanpur district of Chhattisgarh state as they were returning from an anti-Maoist operation.

The rebels, also known as Naxalites, have ambushed police, destroyed government offices and abducted officials.

They have also blown up train tracks, attacked prisons to free their comrades and stolen weapons from police and paramilitary warehouses to arm themselves.