Police arrested a man on Saturday in connection with the macabre murder of two French students who were bound and stabbed repeatedly in a case which has shocked the British capital.

French newspapers said the brutal double murder last Sunday highlighted the knife culture of a city suffering from a spate of fatal teen street stabbings this year.

The victims, both 23, were stabbed scores of times at an apartment in southeast London which was then set ablaze in what police said was one of the most "frenzied, brutal and horrific" murders investigated by Scotland Yard.

Laurent Bonomo was stabbed about 200 times, with up to 80 wounds after he was dead. Gabriel Ferez was knifed 50 times.

Police arrested a 21-year-old man in the early hours of Saturday in southeast London and he was taken into custody at a local police station.

No further details about the man were released.

The murders grabbed headlines in France with daily tabloid France-Soir saying London was becoming one of Europe's most dangerous cities. Another paper, Liberation, said the murders were "the latest examples of a culture of stabbings in London".

A spate of 18 fatal stabbings of teenagers in London has shocked the city with new Mayor Boris Johnson vowing to make the capital a safer place and police expanding a knife crime unit.

In the latest teenage killing, Shakilus Townsend was ambushed by masked teenage boys who attacked him with a baseball bat and a knife while a girl gang member looked on. As he lay dying on a street in south London, he called out for his mother.

London police have arrested more than 1,200 people and seized 528 knives during a six-week crackdown sparked by the growing number of teenage stabbings.

POLICE INQUIRY

Police on Saturday asked people to look out for two new Sony portable play stations which were stolen from the south London flat on the day of the double murder and there was media speculation the two victims were tortured to reveal the PIN numbers of their bank cards.

The explosion that alerted neighbours was caused by a fire accelerant that police believe was used to destroy evidence of the attack in which the science students were bound to chairs.

The pair were to return home this month after a three-month internship studying DNA at Imperial College London.

Police are investigating a possible link between the murders and a burglary at the apartment a week earlier in which a laptop computer was stolen. Experts found no evidence of forced entry on Sunday, suggesting keys might have been stolen earlier.

Police have received about 25 calls from the public and are hunting a white man seen fleeing the scene. Bouquets of flowers were being laid at the murder scene on Saturday.

Claude-Gilles Dussap, director of the Ecole Polytechnique de Clermont Ferrand, where the victims were in the second year of a three-year master's degree, told the Daily Mail: "I have had a number of calls from families saying they are scared about their son or daughter and want them to come home. They think London is dangerous."

Clermont Ferrand is one of France's most prestigious scientific institutions, and Dussap said of the students: "They were brilliant students, the ones you know will go on to great things. They were well-known and well-liked."