Insurgents in India's Manipur state have carried out a deadly attack on security forces, using drones to drop explosives in what police called a "significant escalation" of violence in the restive northeastern region.

A 31-year-old women was killed and six people were wounded Sunday in what police said was an "unprecedented attack" by rebels who used drones to drop the heads of rocket-propelled grenades.

Fighting broke out in Manipur in May 2023 between the predominantly Hindu Meitei majority and mainly Christian Kuki community, an ethnic conflict that has since killed at least 200 people.

Rival militias have set up blockades in parts of the state, which borders war-torn Myanmar.

Longstanding tensions between the two groups revolve around competition for land and public jobs, with rights activists accusing local leaders of exacerbating ethnic divisions for political gain.

"While drone bombs have commonly been used in general warfare, this recent deployment of drones to deploy explosives against security forces and the civilians marks a significant escalation," Manipur police said in a statement Sunday.

The attack outside the state capital Imphal was carried out by "alleged Kuki" rebels, the statement said.

Those injured included an eight-year-old girl -- the daughter of the woman who was killed -- as well three civilians and two police officers.

"The involvement of highly trained professionals, possibly with technical expertise and support, cannot be ruled out," the police said.