Although Japan has made strides through new legislation in recent years to protect foreign nationals from being trafficked into its territory, more needs to be done to increase the number of those actually prosecuted for such crimes, a U.N. official said in a recent interview.

Antonio Maria Costa, executive director of the U.N. Office on Drugs and Crime, said Japan had arrested dozens and convicted 24 traffickers between 2005 and 2007 since introducing legislation that makes buying or selling humans an offense in 2005.

Of those convicted, five were sentenced to less than two years in prison, 12 for two to three years and the remaining seven for more than three years, Costa said. He was referring to data in the "Global Report on Trafficking in Persons," the first assessment by the United Nations of the global human-trafficking situation, released Thursday.