Turkey summoned the U.S. ambassador to Ankara on Monday to lodge a formal complaint with the U.S. for how it handled a brawl outside the Turkish Embassy in Washington, D.C., last week. Protesters who were demonstrating against the visit of President Recep Tayyip Erdogan were beaten by members of his security detail, though it’s still unclear how the fight started. Nearly a dozen people were injured, and the incident has threatened an already tense diplomatic relationship.

Turkey’s complaint comes days after the U.S. summoned the country’s ambassador to Washington, and after several prominent U.S. lawmakers, including Arizona Senator John McCain, called on the U.S. to kick out the Turkish envoy. “We should throw the Turkish ambassador out of the country, we should identify those people that performed these unlawful acts of beating people up and they should be charged,” McCain said.

Summoning the U.S. ambassador John Bass is a way for Turkey to lodge a formal complaint, but it also threatens to make an already-tense situation worse. Last week, Erdogan visited Trump with little official controversy, despite Trump’s decision earlier this month to arm Syrian Kurds, whom the Turkish government sees as terrorists. But protesters had gathered outside the embassy during Erdogan’s visit to denounce his growing authoritarianism. The president has cracked down on dissenters since the failed coup to oust him last year, and reports say about 50,000 have been arrested.