ANKARA (Reuters) - President Tayyip Erdogan described as scandalous a U.S. grand jury’s indictment of Turkish security officials involved in street fighting with protesters during his visit to Washington in May.

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Eleven people were hurt in what Washington’s police chief described as a brutal attack on peaceful demonstrators outside the Turkish ambassador’s residence. Ankara blamed the violence on groups linked to Kurdish militants fighting an armed campaign in southeastern Turkey.

“This is a complete scandal,” Erdogan told reporters after prayers for the Muslim Eid al-Adha celebration. “It is a scandalous sign of how justice works in the United States.”

On Tuesday, a U.S. grand jury indicted 19 people, including 15 Turkish security officials, over the brawl between protesters and Erdogan’s security personnel.

Erdogan said the indictment against members of his security detail, who have since returned to Turkey, was not binding for Ankara.

The skirmish, caught on video, has further strained bilateral ties at a time when the NATO allies are in sharp disagreement over policy in Syria.

Erdogan said the United States had failed to provide him protection from members of the PKK during his visit.

U.S. Secretary of State Rex Tillerson said in a statement the charges sent a clear message that the United States “does not tolerate individuals who use intimidation and violence to stifle freedom of speech and legitimate political expression.”

Since a failed coup attempt last year, Turkey has sacked or suspended more than 150,000 officials in purges, while sending to jail pending trial some 50,000 people including soldiers, police, civil servants.

The crackdown has targeted people who authorities say are suspected of links to the network of U.S.-based Muslim cleric Fethullah Gulen. Ankara blames Gulen for the coup. He denies any involvement.

“These developments in the United States are not good at all,” Erdogan said. “The United States is still a country where the FETO gang (Gulen’s network) is being protected. The United States has literally become a country where the PKK terrorist organization is under protection.

“I am having trouble understanding what the United States is trying to do with all these developments.”