The people attacked the NSCN(IM) camp and set in on fire at 7.30 am with the cadres being chased away, district Superintendent of Police N B S Chumrengthung told PTI.
One person was injured in the leg by gunshots in the melee, he said, adding that casualties on the NSCN(IM) side could not be ascertained.
Chumrengthung confirmed that one civilian was killed on the first day of the clash on December 28.
Home Minister G Kaito Aye said, "It was good that the NSCN(IM) cadres vacated the camp before the issue turned worse."
More From This Section
He said that in the interest of restoring peace and harmony in the state, the government had suggested that the cadres vacate the camp while appealing to the people to shun violence.
He said that the police registered a case for the alleged attemped rape and molestation on December 21 and also issued arrest warrants against the accused, who were cadres of NSCN(IM).
The Sumi people had given a deadline to the NSCN(IM) to hand over the four accused cadres to the district authorities by Christmas day.
When the NSCN(IM) did not respond, the Sumi Hoho, an apex body of the district, announced a 'Flush Out Mission' on December 28.