The U.S. State Department issued a statement Wednesday saying it is “concerned by the violent incidents involving protesters and Turkish security personnel” after a bloody brawl took place in the Turkish Ambassador’s front yard in Washington D.C. between security staff from the Turkish Embassy and President Recep Tayyip Erdogan.

An observer of the rumble said it all started when someone threw a bottle, prompting a clash that left nine injured, including Turkish security guards, and led to two arrests, according to ABC.

After the scuffle, the Turkish embassy stated,”Groups affiliated with the PKK, which the U.S. and Turkey have designated as a terrorist organization, gathered yesterday without permit in Sheridan Circle in the immediate vicinity of the Ambassador’s Residence, while the President of Turkey was visiting the Residence. The demonstrators began aggressively provoking Turkish-American citizens who had peacefully assembled to greet the President.”

Although the PKK is listed as a terror group by the U.S., Russia and other countries urge de-listing the group due to their efforts fighting ISIS.

Thursday, president Erdogan vowed to strike back against U.S. backed Kurdish forces if they threaten Turkey’s security, according to wsoctv.com.

“We said we would not be in such an operation with you where you ally with terror organizations and so we said good luck,” Erdogan said, warning Trump he would also strike back against YPG or People’s Protection Units, an extension of the PKK listed as a terror group in Syria that has waged a three-decade-long insurgency against the Turkish state.

“We are already telling you in advance, our rules of engagement give us this authority, we will take such a step and we won’t discuss it or consult with anyone. Because we have no time to lose,” Erdogan taunted before threatening Trump with Turkey launching a cross-border offensive attack similar to it launched against IS and the YPG in Syria last year.

“We won’t hesitate to launch similar operations if we see the need.”

A cease-fire ended in July 2015 after a two-year fighting hiatus, leading to twenty-four hour curfews and airstrikes on alleged PKK camps in northern Iraq.

Earlier last year, Amnesty International’s Europe and Central Asia’s Program Director John Dalhuisen argued, “the operations currently being conducted under round-the-clock curfews are putting the lives of tens of thousands of people at risk and are beginning to resemble collective punishment.”

Anti-Erdogan protest organizer Flint Arthur told CNN there were about 25 protesters and police had them stand across the street from Erdogan supporters before the battle royal unfolds in the Turkish Ambassador’s front yard in Washington D.C.

“A few police officers stood between us,” Flint said.