British police have arrested a suspect in the brutal murders of two French students who were tied up and stabbed scores of times before their bodies were set alight. The killings have shocked a country already worried by a spate of knife attacks involving young people; 18 teenagers have been slain in London this year. Officers detained a 21-year-old man on a street in southeast London at about 3:40 a.m. (0240 GMT) Saturday, police said. He was being held at a London police station. Police would not say whether the arrested man was the prime suspect in the case, and appealed for witnesses to come forward.