One of India’s oldest domestic security threats reared its head on Saturday when militants killed at least 17 people, a dozen of whom were members of India’s ruling political party. The attackers, suspected members of a Maoist insurgent group, ambushed a convoy of Chhattisgarh state party leaders.

“We can confirm 17 deaths. Among those who have been killed are five policemen. The rest are all leaders of the state Congress unit,” Rajinder Kumar Vij, a Chhattisgarh state security official, told Agence France-Presse. Police identified one of the politicians killed in the attack as Mahendra Karma, a state politician who was a leading figure in the fight against leftist insurgents, the Associated Press reported.

The Maoist insurgency in India is decades old. It first coalesced in 1967 when a group of peasants revolted against the government in the village of Naxalbari in the eastern state of West Bengal, demanding policies that would benefit the poor. The movement soon spread, and elements of the insurgency are now present in 20 of the country’s 28 states, especially those in the east like Chhattisgarh, as well as Andhra Pradesh and Jharkhand. Naxalites exercise control over various swaths of land, although most of it is in jungle areas.

Over years of clashes, thousands of security workers, insurgents and civilians have lost their lives.

Throughout its long history, the insurgency has often been weakened by infighting. But Naxalites share a dedication to communist ideals: Today, the movement is generally united under the banner of the Maoist Communist Party of India.

It is no surprise that Karma might have been on the insurgents’ hit list. He was behind the founding of an anti-Naxalite militia called Salwa Judum in 2005. The group has been accused of perpetrating human-rights abuses against suspected insurgents and civilians in eastern India: Human Rights Watch has called Salwa Judum members “state-backed vigilantes responsible for attacking, killing, and forcibly displacing tens of thousands of people in armed operations against Maoist rebels.”

Similar charges have been leveled against Naxalite militants. The ongoing conflict has made Chhattisgarh and the surrounding area a dangerous place for civilians caught in the middle.

The perpetrators of Saturday’s attack fled the scene, and an investigation into the incident is ongoing.