The State Department is investigating charges that Syrian diplomats are spying on Syrian anti-government demonstrators in Washington and other U.S. cities in order to intimidate their relatives in the restive Middle Eastern nation.

Eric Boswell, assistant secretary for diplomatic security, last week summoned Syrian Ambassador Imad Moustapha to air “concerns with the reported actions of certain Syrian Embassy staff in the United States,” the State Department said Friday evening.

“We received reports that Syrian mission personnel under Ambassador Moustapha’s authority have been conducting video and photographic surveillance of people participating in peaceful demonstrations in the United States,” the department said.