The United States was "outraged" late Wednesday over reports that the Syrian government had arrested relatives of opposition delegation members to peace talks in Geneva.
The Assad regime had detained the family members of opposition envoys on accusations of "terrorism," according to a statement from the US State Department.
"We call on the regime to immediately and unconditionally release all those unfairly arrested," State Department spokeswoman Jen Psaki said.
The US condemned the Damascus government's "new behavior" of attempting to "silence dissent".
"By targeting family members of opposition delegates participating in the Geneva talks, the regime is not only defying the international community but also seeking to suppress the legitimate aspirations of the Syrian people," she added.