Maoist rebels have killed 24 Indian policemen in India’s Chhattisgarh state in one of the most violent and deadly attacks on government forces in years. Some reports say between 300 and 500 rebels ambushed a police convoy that was providing security for workers along a road. Police survivors of the attack said that the attackers were well armed with AK-47s and other small arms. The police managed to kill a number of the attackers as they fired indiscriminately.

The Maoist rebels have been fighting a decades-long insurgency against the Indian government, seeking to establish autonomous communist rule inside the country. They have launched numerous attacks against government forces, including one last month that killed 11 officers and a major attack in 2010 that killed 73 Indian policemen.

The attack on Monday left 24 officers dead and seven wounded. It occurred in an area well-known for having a Maoist presence. Rebels frequently choose government infrastructure projects as their targets. Security forces say such projects are especially vulnerable due to the predictability of work.

The rebels, known as Naxalites, have been fighting the government since 1967. Every year, hundreds of civilians, insurgents, and security forces are killed as the Maoists wage a war they claim is being fought on behalf of the tribal people and rural poor. India has deployed tens of thousands of paramilitary soldiers into the regions most affected by the communist insurgency. Some reports say the Maoists have upwards of 20,000 armed fighters spread primarily throughout five Indian states in the eastern part of the country.

Despite a heavy and continuous government presence, the fighting continues, primarily through the hit-and-run-style attacks like those seen on Monday. Some observers say the long-running insurgency can only be curtailed through economic development and investment in the affected regions—exactly the sorts of projects that were attacked by rebels on Monday.

India’s prime minister said on Twitter that the security forces have not died in vain.