In a statement, Karapatan said an independent fact-finding panel should be formed to look into the killing of Marjorie Reynoso, 18; Lito Doydoy, 27; Jonathan Benaro, 16; and Ramon Regase Jr., 17, all of Maco, Compostela Valley.
Karapatan said the team should be composed of representatives from human rights groups, the Catholic Church, local officials of Compotela Valley and the Commission on Human Rights.
The militant group called on Ermita to prosecute elements of the Military Intelligence Group (MIG) who have been initially tagged as suspects in the killing, and asked that the victims families be properly indemnified.
Last Friday, a certain Willy Javier and several men, allegedly belonging to the MIG, arrested the four victims.
Three days later, the activists bodies were found in a shallow grave in Barangay Quarry in Maco, Compostela Valley.
The male victims were found to be only in their underwear and had torture marks, while Reynoso, whose body was on top of the pile of remains, had masking tape on her mouth and appeared to have been strangled.
The male victims also had stab wounds, while Reynoso had two gunshot wounds in the left side of her head.
Benaro and Reynoso were officers of the Sangguniang Kabataan and members of the militant party-list youth group Anak ng Bayan, which is allied with Bayan Muna.
Karapatan said Doydoy belonged to the militant out-of-school youth group Alyansa ng Nagkakaisang Kabataan Para sa Bayan (Anakbayan), an ally of the left-leaning League of Filipino Students (LFS).
Regase was a mere driver of a "skylab," a motorcycle used for transport in Compostela Valley. Benjie Villa and Edith Regalado