However, no one was reported hurt in both the incidents, a senior police official told PTI.
The incident occurred near Dudheda village under Madded police station limits last night when the privatebuswas on its way to Bhopalpatnam from Jagdalpur district headquarters, he said.
A group of armed cadres stopped the vehicle between Dudheda and Gorla villages and asked the passengers to get down. The ultras then set the bus ablaze, he said.
The Naxals also fired at another passenger bus on the same route, but no one was injured in the two incidents.
Security forces were rushed to the spot, he said.
A combing operation has been launched in the region to nab the attackers, police added.