ANKARA, Turkey (AP) — Turkey summoned the U.S. ambassador on Monday to protest what it called “aggressive and unprofessional actions” by American security personnel against Turkish bodyguards in Washington during President Recep Tayyip Erdogan’s visit last week.

The action appeared to be in retaliation to calls in the U.S. for strong action against the Turkish security officers who were seen hitting and kicking protesters outside the Turkish ambassador’s residence in Washington during Erdogan’s visit. A video shared on social media showed Erdogan watching the melee.

Two Turkish bodyguards were briefly detained after the incident but later set free and returned to Turkey. The United States summoned the Turkish ambassador to raise concerns over the altercation, but President Donald Trump’s administration is facing growing calls for a forceful response to the violence by Turkish security officials on American soil.

The incident added to the already strained ties between the U.S. and Turkey — two NATO allies who are at odds over a U.S. policy to back Syrian Kurdish rebels fighting the Islamic State group in Syria. Turkey considers the fighters to be terrorists.

A Turkish Foreign Ministry statement said U.S. Ambassador John Bass was given a “written and verbal protest” over the treatment of two security officers that it said were “contrary to diplomatic rules and practices.” The statement said the two officers were part of Foreign Minister Mevlut Cavusoglu’s security detail.

The Turkish ministry said it had requested that the U.S. authorities conduct “a full investigation of this diplomatic incident.”

Just after news broke that he had been summoned, Ambassador Bass was at the airport in Ankara, where he greeted U.S. Ambassador to the U.N. Nikki Haley as she arrived on a previously scheduled trip.

Last week’s incident wasn’t the first time violence accompanied a visit by a Turkish leader to the U.S. Last year, a similar fight erupted outside a nuclear security summit in Washington, attended by Erdogan.