Imphal, Oct 10 (IANS): At least four insurgents have been killed in Manipur's Thoubal district in a joint operation by the security forces, officials said on Sunday.

Acting on a secret information regarding the presence of militants, a joint operation of the security forces was launched on Saturday in the Hingojang area of Thoubal district.

The area was cordoned off before the gun battle began between the two sides.

"So far, four insurgents have been neutralised. Operations are underway. Further details are awaited," a senior security force official requesting anonymity told IANS.

Meanwhile, protests continued in different parts of Manipur against the assassination of an influential tribal leader and social activist Athuan Abonmai by the extremists on September 22.

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 Manipur Chief Minister N. Biren Singh, 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.

On the request of the Manipur government, the Union Home Ministry earlier this month has asked the National Investigation Agency to probe the assassination of the influential tribal leader and social activist Abonmai.

The Manipur government has suspended 16 policemen including some troopers of Manipur Rifles for their negligence in duty and failure to protect the life of the tribal leader.

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.