The People's Union for Civil Liberties (PUCL) also demanded registering a FIR into the killings.
"...The continuing allegation that the governments in both states have supported and ensured impunity and immunity enjoyed by the police from investigation, there are enough grounds to feel that independent, impartial and credible investigation cannot be done by the police forces themselves into the encounters," the PUCL said in a statement.
"The PUCL, therefore, demands that a judicial enquiry be initiated headed by a sitting Supreme Court or High Court judge into the killings so that the truth of the killings can be brought to light," it said.
The NGO demanded the police to ensure personal safety of Ramakrishna and others.
28 Maoists were killed in an encounter with a joint team of police from the two states in Odisha's Malkangiri district on October 24.