Imphal, Oct 1 : On the request of the Manipur government, the Union Home Ministry (MHA) has asked the National Investigation Agency (NIA) to probe the assassination of an influential tribal leader and social activist Athuan Abonmai on September 22, officials said here on Friday. Manipur Government's Special Secretary (Home) H. Gyan Prakash said in Imphal that following the proposal of the Director General of Police L.M. Khaute, the MHA issued orders on Thursday directing the NIA to take up investigation of the abduction and murder of Abonmai. The Manipur police chief had earlier constituted a committee headed by Radhashyam Singh, Inspector General of Police (Intelligence), with two other IG rank officials K. Kabib and Kamei Angam Romanus as members to probe the killing. The Manipur government has suspended 16 policemen including some troopers of Manipur Rifles over the killing. Abonmai was shot dead soon after he was abducted by armed men from Tamenglong district headquarters on September 22. The policemen allegedly behaved as mere onlookers while Abonmai was being dragged out and bundled into a waiting jeep. After the widespread condemnation of the assassination of Abonmai by suspected militants of the National Socialist Council of Nagalim (Isak-Muivah), Manipur Chief Minister N. Biren Singh had publicly apologised for the police inaction. "I wondered how the morale of the police had lowered to such an extent. Police should have taken swift action and saved the life of Abonmai," said Singh, who also holds the home portfolio. Abonmai, the former president of Zeliangrong Baudi, a tribal-based local council in Tamenglong district and a leader of the Naga People's Front (NPF), had been abducted on September 22 when the Chief Minister, accompanied by his ministerial colleagues, visited the hill district bordering Assam and Nagaland to inaugurate some projects as a part of the state's 'Go to Hills' campaign. According to the police officials, the tribal leader was reportedly abducted while he was on his way to attend the Chief Minister's programme. Local media reports said that 20 armed cadres of a hill-based extremist outfit suspected to be the cadres of NSCN (IM) kidnapped Abonmai near Pallong village. Police are yet to ascertain the motive behind the incident with no militant group claiming responsibility for the abduction and killing of the tribal leader. Many organisations condemned the incident and demanded an explanation from the perpetrators on the motive behind the assassination. Manipur Congress working president Keisham Meghachandra Singh describing Abonmai as the voice of unity and integrity of Manipur, said his assassination must be taken with the utmost seriousness and the perpetrators must be punished. /IANS