The two victims were gang raped at gunpoint by a gang of three after being robbed of Kenyan Shillings 3,000, four mobile phones and other valuables in the attack.
According to the police, the gang had cut through the door before forcing their way in and attempts by the victims to raise alarm were thwarted after the gang threatened to kill them.
Nairobi County police commander Benson Kibui said the victims had moved to the house less than a month ago, and it seems the gang had been monitoring them before they struck.
He added that police have been mobilised to hunt down the attackers.
The two women are admitted in one of the city hospitals where they are undergoing treatment.
Between January and May this year, rape cases in Nairobi has increased to 383 as compared to the 332 in 2012 and 297 in 2011 while defilement cases hit 1,216 in 2013 as compared to the 1,428 in 2012 and 1,291 in 2011.
Police say there is need for more education on the crime for better understanding on its impact on the society.