French students Laurent Bonomo, from Velaux, near Marseille, and Gabriel Ferez, from Prouzel, near Amiens, both 23, were bound, gagged and stabbed to death in a bedsit in south London on Sunday night.

Detectives, who believe they may have been victims of a robb-ery, said two Sony PSP consoles, costing £130 each, were stolen from Mr Bonomo's rented flat.

They fear a set of keys to the flat, stolen in a burglary six days earlier, may have enabled the attacker to surprise his victims.

Officers are also hunting a black Packard Bell laptop taken in the previous burglary while Mr Bonomo was in the shower.

Mr Ferez, who was living in South Norwood, had travelled to spend the evening at his close friend's flat in Sterling Gardens, a quiet cul-de-sac at New Cross, where they were playing computer games.

Det Chief Insp Mick Duthie, leading the investigation, said: "We are keen to hear from anyone who has recently been offered a laptop and two personal games consoles, or knows someone who has unexpectedly come to have them.

"Laurent Bonomo said he was in the shower when he heard a suspicious noise. He found the window of his living room forced open and his laptop was stolen.

"The search of the address is not yet completed, but we have established that two Sony PSPs are missing and believe they were taken during the incident on Sunday when the two men were killed."

Speaking from the scene of the crime, Det Chief Insp Duthie told Sky News: "We still have no clear idea of what has happened and why this has happened to these two men.

"However, with property being stolen this now suggests that the burglary which happened six days prior may well be linked to the murder."

He said they were still trying to establish whether the victims' bank cards were also stolen.

A white man seen running from the address moments after it exploded in flames has not been identified, he added. He urged him to come forward, saying: "The longer it takes to find you the more my suspicion rises."

A pathologist documented 243 separate injuries to the badly-burned bodies, with Mr Bonomo suffering 80 wounds after he died. It is believed the Frenchmen were dead before the fire started.

Neighbours dialled 999 after an explosion blew the windows out and ignited a fierce blaze.

Investigators believe a petrol-like accelerant was poured on or near their bodies, possibly in an attempt to destroy evidence.

Mr Bonomo's fiancée, Mary Bertez, wrote on a social networking site: "My love, we were always together but unfortun-ately I wasn't there that evening.

"I will never stop thinking about you for a second. I had 10 months of a happiness I had never experienced until then.

"Today you are gone. I will try to be as good as you always wanted.

"I will give all the required information to the investigation, my dear, so you can be avenged."

Det Chief Insp Duthie said the victims were "good, honest, hard-working young men; very intelligent, never caused anybody any problems, they were well liked and came from respectable families. This is just a tragedy."

The biochemistry students, in the second year of a three-year Master's degree at the Polytech Clermont-Ferrand in central France, were due to return home later this month.