Sources said preliminary investigations suggest the involvement of a dominant Naga insurgent group in the killings but it was too early to come to a firm conclusion.
Nine people-- eight labourers and one student leader-- were brutally killed and buried in Nagaland's commercial hub Dimapur. The victims were blindfolded with hands tied and shot at from close range and the corpses were stacked atop each other.
Around 1,500 paramilitary personnel were already deployed along the Assam-Nagaland border in Karbi Anglong district from where the victims belong and more troops are expected to be sent soon to check the violence, the sources said.
The killing of the nine people had followed the murder of four Rengma Nagas, including three women, allegedly by Karbi Peoples Liberation Tigers militants. The KPLT attack had come in retaliation of killing of its two cadres allegedly by Naga Rengma Hills Protection Force and torching of several houses were on December 27, the sources said.
A CBI investigation into the incident, as demanded by Assam Chief Minister Tarun Gogoi, could be ordered only when the Nagaland government agrees to it.