A man punched and kicked a woman on her own bed in her Wembley home while a group men stood and watched.
Metropolitan police said that on November 24, at around 3am, the victim and a second woman were woken by banging on the front door of the property in Station Grove.
Officers added the second woman opened the door and saw a man wearing a grey hooded jumper and a balaclava.
She tried to shut the door but the man forced his way inside and was followed by four other men.
The group then ran into the bedroom and the first suspect jumped onto the bed and punched and kicked the victim in the head, while the remaining suspects stood around watching.
The assault lasted for around 15 minutes, after which the men left the property.
Police and London Ambulance Service (LAS) were called and the victim was taken to Northwick Park Hospital, where she was treated for facial injuries.
There have been no arrests since the assault.
Officers have launched an investigation and have been carrying out a number of inquires including CCTV and forensics.
Detective constable Jo Trist, from Brent CID, said: "This was a particularly vicious and terrifying assault on the victim in her own bed.
"The suspects claimed to know her, but as yet we have been unable to identify any motive for the attack.
"I am therefore appealing for any members of the public who may have information to come forward.
"It may be that other residents in the street saw the suspects arrive at or leave the address."
You can contact the investigation team at Wembley on 020 87333 737 or 101.
Or to remain anonymous you can call Crimestoppers on 0800 555 111.
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