The United States government on Thursday imposed sanctions on a clan and its two leaders within Yakuza, an organized crime syndicate in Japan.

The Department of Treasury blacklisted Sumiyoshi-kai, Yakuza's second-largest clan, and its top leader Shigeo Nishiguchi and No. 2 Hareaki Fukuda, a move that freezes all their assets under U.S. jurisdiction and bars American citizens from doing business with them.

The agency accused Yakuza and its crime clans of involving in " serious criminal activities," including weapons trafficking, prostitution, human trafficking, drug trafficking, fraud and money laundering.

U.S. President Barack Obama identified the Yakuza as a significant transnational criminal organization (TCO) in July 2011, and unveiled a strategy to counter the threats posed by crime syndicates like Yakuza, Italy's Camorra, Mexico's Los Zetas and Brothers' Circle, a TCO based in former Soviet Union areas.

The Yamaguchi-gumi, Yakuza's largest clan, and its two leaders have been put under sanctions by the Treasury.

"These efforts are designed to protect the U.S. financial system from the malign influence of transnational criminal organizations and expose the individuals who are supporting or acting on behalf of the Yakuza," the Treasury said in a statement.

"Through this action, we will continue to work toward disrupting the criminal activities of the Yakuza and dismantling its financial network," David Cohen, under secretary of Treasury for terrorism and financial intelligence, was quoted as saying.

"Today's designation of the Sumiyoshi-kai also supports the administration's intensified efforts to combat trafficking in persons given the Yakuza's long-standing involvement in sex trafficking throughout Asia," he added.