An 18-year-old Somali was sentenced Monday to five to nine years by the Tokyo District Court for boarding and attempting to hijack a Bahama-registered oil tanker off the east coast of Africa in March 2011.

The defendant, whose name has been withheld because he is a minor, is one of four Somalis to face trial in Japan under a 2009 antipiracy law. The series of trials is being heard by three professional judges and six citizens under the lay judge system.

The 18-year-old admitted to participating in the assault on the tanker operated by Mitsui O.S.K. Lines Ltd. but said he only aided the other three men.