A senior public prosecutor confirmed to German press that the bodies were those of two adults and three children. The corpses showed gunshot and stab wounds.
A joint statement from the public prosecutor and the police said the two adults were 40 years old, and the three children were four, eight and ten years old.
According to local news reports, the bodies were found in a residential building on Birkenallee in Senzig, a district on the south-east edge of the capital.
Lutz Miersch, a police spokesperson, said: “We assume that this was a homicide”.
The investigation has now been taken over by murder detectives.
Police said that they had received a call about the property around 12pm today.
The person who had called them had reportedly seen a lifeless body in the house, and raised the alarm.
Gernot Bantleon, a senior public prosecutor told German newspaper Bild: “The homicide squad and forensics are at the crime scene in Senzig.
“A public prosecutor from the express service for capital crimes is investigating.
“The five dead people are two adults and three children. The corpses show gunshot and stab wounds.”
The police spokesperson said the road the building was situated on was blocked, and the police investigation ongoing.
Senzig is part of the Königs Wusterhausen area, itself in the Dahme-Spreewald district of Brandenburg.
Additional reporting by Monika Pallenberg