The US Treasury Department has imposed sanctions on 8 Syrian military prisons it says have been the sites of thousands of murders that occurred under the President Bashar Al Assad’s regime.

The Treasury’s Office of Foreign Assets Control (OFAC) on Tuesday also sanctioned five senior officials from Al Assad’s intelligence apparatus who run the detention centres.

“The individuals and entities we are designating today have been a party to gross violations of Syrian human rights, including supervising the torture and killing of detainees,” OFAC Director Andrea Gacki told reporters.

“Bashar Al Assad and his brutal regime continue to extend the dispute in Syria by their brutal treatment of prisoners who oppose the regime’s oppressive policies and murderous activities.”

Gacki added that the prisons “have been the site of horrific torture and thousands of murders”.

She referenced the famous caches of grisly photos smuggled out of the country by “Caesar”, a regime defector who once worked as a photographer for the Syrian military.

Many of the sanctioned prisons are operated as branches of the Syrian Military Intelligence and the Syrian General Intelligence Directorate, Ms Gacki said.

In a statement, OFAC highlighted abuses at the Saidnaya military prison, which has a well-documented history of serious human rights horrors.

“Two buildings at the Saidnaya military prison site alone could contain as many as 10,000 to 20,000 detainees between them,” the statement read.