Arsema Dawit is the latest name on a somber list.

The 15-year-old schoolgirl was found dead in an elevator at a south London apartment building this week, the 16th teenager slain in Britain's capital this year. Most, like Dawit, were stabbed to death — and most of their killers were other young people.

The deaths have sparked fears of a knife crime "epidemic" among Britain's young, and spurred the government to announce tougher penalties for teens caught carrying a blade.

"Carrying a knife is completely unacceptable," Prime Minister Gordon Brown said Thursday announcing an end to Britain's system of issuing warnings to some teenagers caught with knives.

Until now, warnings were given to most of those under the age of 18 found with knives. With the change, anyone 16 or over who carries a knife with a blade longer than 3 inches will be prosecuted. Those convicted face a penalty of up to four years in prison.

"Young people need to understand that carrying knives doesn't protect you, it does the opposite — it increases the danger for all of us, destroys young lives and ruins families," Brown said.

For a major city, London has a low murder rate. Police say there were 159 homicides from April 2007 to the same month this year, about a third the number in similarly sized New York. But the number of victims under age 18 has risen. According to police figures, 17 teenagers were killed in London in 2006, 27 in 2007, and 16 so far this year. Eleven of the 16 were stabbed to death.

Many young people say pressure to carry — and use — knives is growing.

"It's increasing. It's stupid things like 'you have spoken to my girlfriend, I'll slash you up,' or 'If I see him out, he's having it,'" said Monique Morrison, 21, one of a group of young people who met with the prime minister Thursday to discuss the problem.

The grim regularity of stabbings over the past few months has alarmed Londoners.

The victims include 18-year-old Rob Knox, who had a small part in the upcoming film "Harry Potter And The Half-Blood Prince," and was stabbed to death while trying to break up a brawl outside a south London bar on May 24. A 21-year-old has been charged with his murder.

Knox's smiling photo and his grieving parents appeared on the front of newspapers and on television news bulletins. Two weeks earlier, it had been the face and the family of Jimmy Mizen, a popular 16-year-old stabbed with a piece of glass outside a bakery. A 19-year-old is accused of his murder.

A 21-year-old student has been charged with killing Dawit, an Eritrean immigrant who sang in a church choir and had complained to police about an earlier assault.

"It's not even a shock anymore" to hear about stabbings, said 16-year-old Vogue Huell, a student from Bromley, the south London district where Knox was killed. "It's the whole gang culture, I think. As soon as one person gets stabbed, someone goes after another person."

London's new mayor, Boris Johnson, has also vowed to crack down on knife crime. His proposals include airport-style metal-detecting arches at train and subway stations. London police recently began an aggressive new program to search anyone they wish for knives without having to justify their suspicions beforehand.

Some experts, however, say the measures are little more than political posturing.

"I'm skeptical about whether the latest measures will have an effect," said Enver Solomon, deputy director of the Center for Crime and Justice Studies at King's College London.

He said most teens who carry knives do so because they have been the victims of crime.

"The clear message from research is that kids carry knives because they don't feel safe," Solomon said. "Unless you address that feeling of insecurity, you are not going to have a big impact on the number of kids carrying knives."