Fifteen Asian women on Monday filed a class-action lawsuit against the Japanese government in the United States, claiming they were forced to serve as sex slaves for the Imperial Japanese military during and before World War II.

Former wartime sex slaves from South Korea protest on Monday in front of the Japanese Embassy in Washington.

The plaintiffs -- six Koreans, four Chinese, four Filipinos and one Taiwanese -- filed the case with a federal district court in Washington to seek compensation and an official apology from the Japanese government.

"We have with us here today survivors of a premeditated systemic plan originated and implemented by the government of Japan to enslave women considered inferior and subject them to repeated mass rapes," Michael Hausfeld, an attorney representing the plaintiffs, told a news conference to announce the legal action.

"Now, with the recent availability of documentation, the offenders should be held accountable," he said.