The number of fatal stabbings in London this year has risen to over 50 with four more cases in a single day, but police said yesterday the city was not suffering an epidemic of knife crime. One of the latest victims to die in four separate incidents in London on Thursday was aged 19 - the 20th teenager to have died violently in the capital this year.

Before the latest four slayings, 49 people had died of knife wounds this year in London, a spate of violence that has alarmed politicians and the news media.

Violence in the British capital has become an international issue after the frenzied stabbings of two French students in London last week, an incident police said was one of the grisliest cases they had seen.

The police say tackling knife crime has overtaken terrorism as their number one priority. They have set up a 75-strong team to target those carrying weapons.

"I wouldn't describe it as an epidemic," a police spokesman said after the latest killings.

"There is an issue with knives and that is why we have launched Operation Blunt 2," he added, referring to a six-week campaign in which officers have searched 27,000 people, arrested more than 1,200 and seized 500 knives in London.

Sir Ian Blair, head of London's Metropolitan Police Service, said detectives had made arrests in three of the four latest murders.

"I want to reassure the public that the MPS is doing everything possible both in terms of thoroughly investigating each case and in continuing to carry out proactive operations to get knives off the streets," he said.

Authorities have warned teenagers that carrying a knife makes them more at risk, not safer, because of the danger the weapon will be used against them.

Police say that London is still safe for a city of its size, and that the overall murder rate has not risen substantially. In the year ending in May this year there were 162 murders. There were 155 the previous year, and 210 five years ago.

New York, a city of similar size and wealth, had 496 murders last year, and as many as 2,262 during the crack cocaine epidemic in 1990.

But the large number of teenage stab victims in London this year has captured the public imagination, as did the particularly vicious slaying of the French students.

In a case described by officers as one of the most brutal they have seen, French bio-engineering students Laurent Bonomo and Gabriel Ferez, both 23, were bound, gagged and repeatedly stabbed in Bonomo's south London apartment last week.

Mr Bonomo was stabbed nearly 200 times, with up to 80 of the wounds inflicted after he was dead. Mr Ferez had nearly 50 knife wounds. The killer or killers then set fire to the apartment in an attempt to destroy evidence. On Thursday, the police arrested a fourth suspect in the case. Daniel Sonnex, 23, was detained in south London less than an hour after Scotland Yard issued a call for information on his whereabouts and described him as dangerous.