Woori Bank and the Industrial Bank of Korea have apparently severed ties with Iran's state-run Bank Tejarat following U.S. Treasury Department sanctions against the Iranian bank. According to financial industry sources Tuesday, the two banks halted financial transactions with Bank Tejarat on Jan. 23.

Bank Tejarat is the third-largest in Iran and specializes in export and import financing. The U.S. government blacklisted it last month citing links to other financial institutions in Iran that were allegedly involved in the country's nuclear weapons program.

This is the second time Korean banks have severed ties with an Iranian bank since July 2010 after U.S. sanctions went into effect. At the time, financial authorities in Korea shut down Bank Mellat's branch office in Seoul.