WASHINGTON (AP) — The Treasury Department is cracking down on supporters of Syrian President Bashar Assad, slapping sanctions on three leaders of the Hezbollah militant group and a Lebanese businessman for their suspected militant activities in the war-torn country.

Last month, Treasury took action against front companies and individuals suspected of facilitating the Lebanese Hezbollah militant group, which began providing military support to the Assad government when the Syrian conflict began in 2011.

On Tuesday, Treasury sanctioned Mustafa Badr al Din (muh-STAF-ah BAH-der al DEEN), Fu ad Shukr (foo-AHD SHOO-krah) and Ibrahim Aqil (EE-BRA-HEEM ah-KEEL) for acting on behalf of Hezbollah. Also sanctioned was Lebanese businessman Abd al Nur Shalan (AB dah al noor Sha-LAHN),

The action freezes the U.S. assets of all four and prevents Americans from engaging in transactions with them.