"Japan should immediately implement effective administrative mechanisms to provide full reparations to all survivors and remove legal barriers toward bringing claims before Japanese courts by reforming national laws," Purna Sen, director of the London-based human rights watchdog's Asia-Pacific Program, said Friday.

He made the remarks at a press conference in Bangkok to launch a report titled "Still Waiting After 60 years: Justice for Survivors of Japan's Military Sexual Slavery System."

Amnesty estimates that up to 200,000 women from China, the Korean Peninsula, the Philippines, Indonesia, Malaysia, Vietnam and the Netherlands were sexually enslaved by the Japanese military before and during World War II. Many were less than 20 years old, and some were as young as 12.

The Amnesty report says the government denied responsibility for the "comfort women" system until direct evidence was discovered by professor Yoshimi Yoshiaki in 1992. In 1993, it admitted the military had forced Asian women to serve as sex slaves and offered an apology.

But it has consistently refused to pay direct compensation to individual victims, saying all war claims were officially settled by postwar treaties.