Naxal pamphlets purportedly from the 'Maharashtra, Madhya Pradesh and Chhattisgarh special zonal committee' of the outlawed movement proclaiming that deaths of three ultras in police encounters would be avenged were found in Balaghat in Madhya Pradesh, an official said on Monday.
Naxal Sharda (25), with a reward of Rs 8 lakh on her head, was killed last month, while Manjesh (30) and Nanda (22) were shot dead in July last year, officials said.
All three were from neighbouring Chhattisgarh.
The handouts warned that police informers would be executed in public.
Meanwhile, Balaghat Zone Inspector General of Police KP Venkateshwar Rao said his force had knowledge of the development and security had been beefed up accordingly in the area, over 430 kilometres from the state capital.