Xi Zhou and her boyfriend Zhen Xing Yang studied at Newcastle University
A Chinese man who was murdered along with his girlfriend in Newcastle may have been tortured before he died.
Zhen Xing Yang and Xi Zhou, both 25, died after a "frenzied" knife attack in a flat in the city's West End.
Police say Zhen Xing Yang was "assaulted for more than an hour" before being stabbed. They believe passers-by may have heard his screams.
A cat's body, found hidden under a sink in the flat, could also provide clues into the motive behind the murders.
The cat, which was found submerged under water in a washing bowl, was possibly killed by the pair's attackers, said Northumbria Police.
A post-mortem revealed that Zhen Xing Yang suffered extensive bruising to his arms before he died.
Examinations also showed Xi Zhou may have been asphyxiated as well as stabbed during the attack.
Their bodies were found at the downstairs flat on Croydon Road on Saturday afternoon.
Det Supt Steve Wade, leading the investigation, said: "The assault has probably gone on for an hour or more prior to death and in that respect you would imagine that people might have heard screams or seen people coming and going from the address."
Det Supt Steve Wade's news conference
He added: "The bathroom of the house has been searched and in a washing bowl underneath a sink was the body of a mature cat.
"The washing bowl had been filled with water and resting on top of the washing bowl, and therefore concealing the body of the cat, was towelling and kitchen gloves.
"Officers are keeping an open mind as to the significance of this find. However one possibility being considered is the cat has been killed by those responsible for the murders."
Mr Wade said it was likely that whoever carried out the murders would have left the scene heavily bloodstained.
Both victims had wounds consistent with trying to defend themselves.
The couple met at Newcastle University where they both took MAs, graduating in September 2006.
Since then Xi Zhou, known as Cici, had worked as a waitress at the Wagamama restaurant in Newcastle.
Police have not yet established Zhen Xing Yang's occupation, despite looking at the couple's bank accounts.
They have ruled out any Triad link, or drugs links, and said the murders remained motiveless.
Detectives confirmed on Tuesday that they had traced Zhen Xing Yang's mother to Dalian City in China and informed her of her son's death.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.