Police arrested businessman Sheikh Shaukat and his three young sons in Faisal Town area on a complaint of Shamim Bibi, mother of victim Azra.
The police said they did not rule out the possibility of rape before the murder.
Superintendent Tariq Aziz said the police responded to a call from Shaukat's residence yesterday and found the girl's body on stairs leading to the roof.
"A piece of cloth was found close to the body and marks of strangulation were also spotted on her neck," Aziz said.
The police officer said the autopsy would determine the exact cause of Azra's death.
Last week, a 10-year-old maid had been brutally tortured to death here allegedly by her employers for "stealing" 100 rupees.