Secretary of State Rex Tillerson on Sunday denounced a violent clash in Washington last week involving Turkish security personnel and protesters, as the administration faced political pressure to respond.

In an interview on "Fox News Sunday," Tillerson said the State Department had called in the ambassador of Turkey to discuss the incident and saying, "that this is simply unacceptable."

"There is an ongoing investigation," he said. "We'll wait and see what the outcome of that investigation is. But we have expressed our dismay at what occurred at the Turkish Embassy."

On May 17, a demonstration staged to protest Turkish President Recep Tayyip Erdogan’s official visit to the United States turned bloody when a pro-Erdogan group attacked demonstrators at Sheridan Circle near the residence of the Turkish Ambassador to the U.S. Nine people were hurt and two arrests were made during an altercation.

Sen. John McCain has called for the Turkish ambassador to be expelled. The incident occurred last Tuesday during protests surrounding a visit by Turkish President Recep Tayyip Erdogan.