The forest ranger's office in Tuibong was set on fire around midnight, said police.
A government building was set on fire in Manipur's Churachandpur district on Saturday, two days after a gym was vandalised ahead of its inauguration by Chief Minister N Biren Singh.
The district administration has imposed a night curfew in the district from 5 pm to 5 am for an indefinite period as the situation remained tense.
Several fire engines were pressed into service after protesters set the forest ranger's office in Tuibong on fire around midnight, said police.
Incidents of violence have also been reported from the tribal-dominated Kangpokpi and Tengnoupal district since Friday night, police said.
Director General of Police P Doungel and senior officials on Saturday visited Churachandpur and reviewed the situation in the southern part of the state.
The situation remains grim and heavy security measures have been taken to prevent fresh incidents of violence, said a police official in state capital Imphal.
In Thursday's incident, a mob set an open gym on fire, damaged chairs and other materials, and threw stones at the security forces, forcing them to use tear gas to disperse the mob in the bandh-hit town. But no major injury was reported.
The police have blamed illegal immigrants from Myanmar for the arson.
Chief Minister N Biren Singh, who was set to inaugurate the gym and address a public gathering in the town on Friday, cancelled his visit.
The Indigenous Tribal Leaders' Forum (ITLF) had called an eight-hour shutdown in Churachandpur on Friday to protest an eviction drive in the protected and reserve forests.
They had also organised rallies against the eviction drives in March in three districts, Churachandpur, Kangpokpi and Tengnoupa, during which five people were injured.
Meanwhile, the Chief Minister reiterated that poppy cultivation will completely wiped out in the state and his government is committed to protect people from drug menace.
The BJP government in the state would not allow poppy cultivation and has been taking continued actions against those involved in such plantations, he said, assuring action against the trouble-makers.
Veteran Congress leader and three-time former Chief Minister Okram Ibobi Singh and state Congress chief K Meghachandra Singh strongly criticised the BJP government for the "wrong policy in dealing with tribals and forest lands."
Kuki Students' Organisation has also come out in support of the forum and condemned "undermining tribal rights including demolition of religious centres and illegally evicting tribal villages."
Earlier this month, the state government demolished three churches claiming that they were "illegal constructions".
The hilly and forested Churachandpur district in southern Manipur, which borders Myanmar and Mizoram, is home to various Kuki-Chin insurgent groups.