The number of fatal stabbings in London this year has risen to over 50 with four more cases in a single day, but Scotland Yard said on Friday the city is 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.

Up to July 7, 49 people had died from stab wounds in London this year. Police were unable to provide comparative figures for last year, though between April 2007 and March 2008 there were 160 homicides, 72 of which were stabbings.

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

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

"There is an issue with knives and that is why we have launched Operation Blunt 2," he added, referring to a Met crackdown on knives.

The spate of stabbings prompted Met chief Ian Blair to release a statement on Friday in an attempt to reassure the city's population.

Detectives had made arrests in three of the four murders, he said.

"I want to reassure the public that (police) are 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 added.

The latest 19-year-old victim died after suffering multiple stab wounds in Edmonton, north London, while two men in their 20s were killed in attacks in Leyton and Walthamstow in east London, with the fourth victim - a man in his 40s - knifed in Tottenham.

As well as probing those deaths, Scotland Yard is running a major investigation into the murders of two French students killed last week in one of the most brutal stabbings officers say they have to deal with.