Tawang Deputy Commissioner (DC) Kemo Lollen said the 15-year-old girl, a student of Government High School, Tawang, and resident of Lhou village, went missing on August 28.
Later that night, police recovered her body without clothes and bearing head injury from Shyro village located near Tawang town.
Eight students, including a girl, of the same school have been arrested in connection with the incident, official sources said.
Angry citizens yesterday gheraoed the office of the Deputy Commissioner and the Tawang police station demanding that the authorities hand over the arrested to them.
The mob allegedly pelted stones at the DC's office and partially damaged an official vehicle, the sources said.
The citizens also vandalised a BRTF labour house suspecting their involvement in the murder, they said.
Also Read
The locals are also expected to take out a candlelight march today to express solidarity with the bereaved family.
Meanwhile, Lollen said the situation in Tawang was under control for now.
This is the first such incident in Tawang, known as the most peaceful district of the state.
It comes in the wake of the murder of a girl at Yazali recently and attack on woman journalist Tongam Rina by an unidentified gunman in Itanagar on July 15.