WASHINGTON (Reuters) - The United States said on Wednesday (May 17) it was voicing its "strongest possible" concern to Turkey over a street brawl that erupted between protesters and Turkish security personnel during President Tayyip Erdogan's visit to Washington, DC.

Turkey blamed the violence outside its ambassador's residence on demonstrators linked to the Kurdistan Workers Party (PKK), but Washington's police chief called it a "brutal attack"on peaceful protesters.

Police said 11 people were injured, including a Washington police officer, and two people were arrested for assault. At least one of those arrested was a protester.

"We are communicating our concern to the Turkish government in the strongest possible terms," State Department spokesman Heather Nauert said in a statement.

A video posted online showed men in dark suits chasing anti-government protesters and punching and kicking them as police intervened. Two men were bloodied from head wounds as bystanders assisted dazed protesters.

Washington police chief Peter Newsham told a news conference on Wednesday that police had a good idea of most of the assailants' identities and were investigating with the Secret Service and State Department.

One of the men arrested, Jalal Kheirabadi, told Reuters he was being beaten by three or four people when a DC police officer accused him of assault. He spoke by phone on Wednesday night after he was released pending a June court hearing.

Kheirabadi, 42, of Fairfax, Virginia, said he attended the protest to urge the US to continue its support for Kurdish forces in Syria. He said he remembered being punched by three or four of Mr Erdogan's guards and seeing a DC police officer fall, but he did not recall hitting the officer.

"He stood up and protected me from them, and then he handcuffed me. He was a real gentleman, I appreciated that,"said Kheirabadi, adding that he immediately apologised to the officer.

Kheirabadi said he has lived in the US for 13 years with his family, including a young son, and had never been in legal trouble in the US before his arrest. "I didn't go there to fight," he said. "It just happened."

A charging document for the other man arrested, Ayten Necmi, 49, of Woodside, New York, said peaceful protesters were taunted by a second group of demonstrators who shouted obscenities and taunts at them.

The document said four or five Middle Eastern men in dark suits from the second group assaulted the peaceful protesters. It said about eight people told officers they were attacked, thrown on the ground and stomped.

The Turkish Embassy said in a statement the protesters were affiliated with the outlawed PKK. The group is considered a terrorist group by both Turkey and the US.

The embassy said Mr Erdogan was in the ambassador's residence after meeting President Donald Trump, and Turkish-Americans who were there to greet him responded to provocations from PKK-linked protesters.

"The violence and injuries were the result of this unpermitted, provocative demonstration," the statement said. The claim that protesters were linked to the PKK could not be verified immediately by Reuters.

Tens of thousands of Turks have been detained as Mr Erdogan cracked down on the media and academia following an attempted coup in 2016. Mr Trump made no mention on Tuesday of Mr Erdogan's record on dissent and free speech.

House of Representatives Foreign Affairs Committee chairman Ed Royce, a California Republican, called on Attorney-General Jeff Sessions and Secretary of State Rex Tillerson "to hold individuals accountable" for the attack.

Washington mayor Muriel Bowser and five Republican senators, including Mr John McCain of Arizona and Mr Marco Rubio of Florida, also condemned the assault.

Mr Mehmet Tankan, 31, said he was one of a dozen protesters outside the ambassador's residence chanting anti-Erdogan slogans when the brawl broke out.

Tankan said by telephone seven security personnel, some carrying firearms, rushed up and began punching him, bruising him all over his body.

He said the violence was worse than when Mr Erdogan visited Washington in 2016 and scuffles erupted between his security detail and demonstrators.

"The next time they could kill us easily. I'm scared now too, because I don't know how it will affect my life here in the United States," said Mr Tankan, who lives in Arlington, Virginia.