Suspected Maoist rebels attacked a convoy of local Congress party workers and leaders on Saturday, killing at least 24 people in the deadliest assault amid a long-simmering conflict between insurgents and authorities in central India.

The convoy, carrying state Congress leaders and party workers, were on their way from a political rally in Chhattisgarh state when a land mine exploded before nearly 300 heavily armed gunmen opened fire on them, police said.

The firing continued for almost one and a half hours, an injured Congress worker told India’s NDTV news.

Among those killed were State Congress chief Nandkumar Patel, his son, Dinesh, and local leader Mahendra Karma. The main target of the attack is believed to have been the congress chief, with authorities saying his body was later found mutilated, reports AFP. At least six policemen also died in the attack.

As many as 37 people were wounded, including former federal minister Vidya Charan Shukla, 84, who was in serious condition after sustaining several bullet injuries.

Congress chief Sonia Gandhi rushed to the state capital Raipur along with Prime Minister Manmohan Singh to visit some of the wounded.

Gandhi condemned the attack as a “cowardly act” by the Maoists, also known as Naxalites. The prime minister said India would “never bow down” before the rebels.