CISF will also provide 'Z plus security cover' to RSS chief Mohan Bhagwat, a source in the organisation said.
About 150 personnel, including officers, who arrived last evening replaced the State Reserve Police Force (SRPF) and Nagpur Police which provided security to the Sangh headquarters for last about 15 years, sources said.
The Union Home Ministry had earlier decided to provide RSS HQ and Bhagwat a Z plus security due to the threat perception.
Bhagwat was in Nagpur today, a RSS office-bearer said.
The security personnel are presently accommodated in a school near the headquarters.
In June 2006, three suspected Lashkar-e-Toiba (LeT) militants were gunned down by the police when they tried to enter the RSS HQ.