The U.S. State Department said a clash in Washington this week in which Turkish security personnel apparently attacked demonstrators was “deeply disturbing.” A State Department statement Friday promised a “thorough investigation’’ to hold those responsible accountable. Tom Shannon, the acting deputy secretary of state, met Wednesday with Turkish Ambassador Serdar Kilic to discuss the altercation. “The State Department has raised its concerns about these events at the highest levels,” the statement said. Watch: Turkish President Erdogan Watched Violent Clash Near Embassy The clash broke out Tuesday between Turkish security personnel and protesters outside the Turkish ambassador’s residence during Turkish President Recep Tayyip Erdogan’s visit to Washington. Protesters say they were attacked by Turkish security forces as they demonstrated peacefully. Turkey blamed the clash on the demonstrators, claiming they aggressively provoked people who had gathered to see Erdogan. VOA reporters recorded images at the scene that indicated the Turkish security detail suddenly turned on the demonstrators, knocking them to the ground and kicking them until American police pushed the Turks away. The video showed Erdogan standing beside his limousine, watching the brawl. U.S. officials briefly detained two members of Erdogan’s security detail, but they were soon released, under customary diplomatic protocols granting immunity to aides accompanying a visiting dignitary. Some U.S. lawmakers have demanded the United States take stronger action.