Security officers and a special police unit fanned out through the block in Banovo Brdo, where Darko Mladic - the son of the former Bosnian Serb military commander - lives in the Mladic family home. Reporters were kept away from the area.
Also Friday, two more people were arrested on suspicion of helping the former military commander evade justice, said Belgrade District Court spokeswoman Marina Klaric-Zivkovic.
She could not immediately reveal the identities of the two, but the private Beta news agency said one was believed to be a retired Bosnian Serb army officer.
Police raids earlier in the day that were reported by state-run television appear to have targeted a separate area of the capital.
Police have searched the home of Mladic's son several times in the past, and it was not immediately apparent whether the raids brought authorities any closer to capturing the former general, sought by the U.N. war crimes tribunal in The Hague, Netherlands.
Earlier this week, chief U.N. war crimes prosecutor Carla Del Ponte said that Mladic was hiding in the Belgrade area, changing apartments daily.
The two arrests Friday bring to 10 the total number of people rounded up in recent months on suspicion of assisting Mladic, whose capture has become the main condition before Serbia can be considered for European Union membership.
Belgrade judges ordered three suspected Mladic aides who were arrested Thursday to be held in custody for one month pending an investigation, Klaric-Zivkovic said.
Mladic was indicted by The Hague tribunal on charges of genocide for the massacre of nearly 8,000 Muslim men and boys at Srebrenica and other war crimes stemming from Bosnia's 1992-95 war.
The EU on Wednesday suspended pre-membership negotiations with Serbia-Montenegro after Belgrade missed an April 30 deadline for Mladic's capture.