The Naxals said they also wanted to avenge atrocities on innocent villagers and tribal women during 'Salwa Judum' (anti-Naxal vigilante movement).
In a release to the media, spokesperson of Dandkaranya Vishesh Zonal Committee Gudsa Usendi held both BJP and Congress responsible for "anti-people policies and hence senior politicians were targeted".
The letter categorically states that Karma, Patel and some others were the "main targets" of the attack.
"The purpose was to punish Mahendra Karma who had launched the anti-Naxal armed movement Salwa Judum and some other Congress leaders," the letter said quoting Usendi.
The letter further states that "during Salwa Judum, hundreds of tribal women were allegedly gangraped and several innocent villagers were killed".
"Through this attack, we have taken their revenge," it added.
The Maoists also made several demands in the letter, calling for withdrawal of paramilitary forces from Dandakaranya and release of innocent tribals from prisons.
Heavily armed Maoists ambushed a convoy of Congress leaders in Chhattisgarh's Bastar district on Saturday, killing 27 people including Patel, Karma and ex-MLA Uday Mudliyar besides leaving 36 others injured.
