| Syrian government forces inspect a building in Damascus. |
The Treasury Department announced on Tuesday it has frozen any assets that five Syrian people and five Syrian companies may have in US jurisdictions and has barred Americans from conducting any financial transactions with them.
The department said in a statement the sanctions were due to Syria's "relentless attacks on civilians".
The announcement comes a day after the administration accused Syria of killing thousands of detainees at a military prison and cremating their remains to hide the scale of the killing.
Among those affected by Tuesday's sanctions are Assad cousins Ihab Makhluf and Iyad Makhluf, their family's al-Bustan Charity and the Cham Islamic Bank.