South Korean police said Friday they arrested three foreign students and booked 18 others for either selling or using illegal narcotics. According to the Seoul Metropolitan Police Agency, three foreigners, including an 18-year-old U.S. citizen, were involved in smuggling in cocaine, methamphetamine and hashish from foreign countries last July. The three students under arrest are also charged with selling the drugs to foreign and Korean residents and students in Seoul. Three other foreign students have been booked on the charge of drug transactions, along with 15 others arrested for illegal drug use, police said. The recently nabbed for aged between 16 and 20, currently attending an international high school or language school at a Seoul university, according to the police. 'They didn't seem to feel guilty for their behavior as they had prior experiences of taking drugs overseas,' the police said. 