A diplomatic dispute deepened when Turkey summoned the American ambassador in Ankara to the Ministry of Foreign Affairs Monday, to protest "the aggressive and unprofessional actions taken" by American security personnel against Turkish security officers.

It stems from a violent confrontation that broke out in front of the Turkish ambassador's residence in Washington, D.C., on May 17 — the same day Turkish President Recep Tayyip Erdogan was visiting President Trump at the White House. Video appears to show Erdogan's security forces pushing past D.C.'s Metropolitan Police officers and violently breaking up a group of protesters, knocking down some and repeatedly kicking them in the head. Around a dozen people were injured.

D.C.'s police chief called it "a brutal attack on peaceful protesters."

But now Turkey is requesting that "US authorities conduct a full investigation of this diplomatic incident and provide the necessary explanation."

The day after the incident, the Turkish Embassy blamed it on demonstrators, calling them, "groups affiliated with the PKK, which the U.S. and Turkey have designated as a terrorist organization." The embassy's statement goes on to say, "The demonstrators began aggressively provoking Turkish-American citizens who had peacefully assembled to greet the President. The Turkish-Americans responded in self-defense."

The U.S. State Department took a different stand. It released a statement the same day, sharply condemning what happened and seemingly laying blame on Turkey: "Violence is never an appropriate response to free speech, and we support the rights of people everywhere to free expression and peaceful protest. We are communicating our concern to the Turkish government in the strongest possible terms."

The demonstration was arranged by pro-Kurdish and Armenian groups protesting a range of Erdogan policies.

Under his rule, Turkey has seen a crackdown on freedom of expression, with dozens of media outlets shuttered and an array of judges, journalists and civil servants jailed following last summer's failed coup attempt.

The New York Times reports that Turkey's summoning of Ambassador John Bass appears to be a tit-for-tat response to the State Department's summoning of the Turkish ambassador to Washington.

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