The National Investigation Agency (NIA) on Wednesday filed a chargesheet against 23 accused persons — including CPI(Maoist) general secretary Namballa Keshav Rao, his predecessor Mupalla Laxaman Rao alias Ganpati, and several other politburo members — in a case relating to a Maoist attack dated April 3, 2021, on a police party in Bijapur, Chhattisgarh, which killed 22 police personnel.