Washington on Monday announced sanctions targeting members of an Islamic State cell operating in South Africa as well as companies they control, in retaliation for their support of the terrorist group.

The Treasury Department said the aim is to choke off support for the network and stem the expansion in the region.

"Today, Treasury is targeting key individuals in ISIS's network in South Africa, as well as their business assets, who have played pivotal roles in enabling terrorism and other criminal activities in the region," said Brian E. Nelson, Treasury's top terrorist finance watchdog.

The move blacklists four individuals and eight companies, freezing any US assets and denying them the ability to use the US financial system.

"The United States, as part of the Global Coalition to Defeat ISIS, will continue to partner with South Africa to deny ISIS the ability to exploit the country’s economy to raise and move funds to support the growth of ISIS affiliates and networks," Nelson said in a statement.

The sanctions target members of the Durban, South Africa-based ISIS cell led by Farhad Hoomer, who was previously targeted by sanctions. They are brothers Nufael Akbar and Yunus Mohamad Akbar, as well as Mohamad Akbar and Umar Akbar.

The companies hit with sanctions are MA Gold Traders (PTY) LTD, Bailey Holdings (PTY) LTD, Flexoseal Waterproofing Solutions (PTY) LTD, HJ Bannister Construction CC, Sultans Construction CC, Ashiq Jewellers CC, Ineos Trading (PTY) LTD, and Shaahista Shoes CC.