Newsham urged those being sought and some still unidentified to surrender, speaking a day after two other people were arrested in the case. Narin is expected to be in D.C. Superior Court on Wednesday; Yildirim was awaiting extradition from New Jersey. They include two Canadians and four Americans, according to prosecutors.
Earlier Wednesday, two Turkish men living in the U.S. had been arrested for their role in beating protesters outside the Turkish embassy on May 16.
Eleven people were hurt in the fracas, nine of whom needed hospital treatment.
At the time, two men were arrested and charged with simple assault.
Now, the Metropolitan Police Department has announced that 18 people are facing charges in connection to the brawl outside the Turkish ambassador's residence during a visit by Turkish President Recep Tayyip Erdogan.
The Turkish government has blamed the violence on the protesters, whom they allege were linked with the PKK, considered a terrorist group by the U.S.More news: Firefighters battling massive blaze in London high-rise
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Some critics were angry police did not make more arrests on the spot; the State Department ordered a federal police agency to release two presidential guards taken into custody saying they had diplomatic immunity.
"We are hopeful that those responsible will do their part and present themselves to answer to these charges", Newsham said. When asked what about those who aren't law-abiding, he added, "That remains to be seen". Video shows Erdogan watching the brawl go down, if not ordering it.
United States officials on Wednesday arrested two protesters who were allegedly involved in the clash outside the Turkish ambassador's residence.
The ministry said in a statement that the decision to charge the agents was "wrong, biased and lacks legal basis" and that the melee was actually the fault of USA law enforcement that failed to take necessary security steps.
The Turkish Embassy did not immediately respond to a request for comment.
At least one senior Republican welcomed the news of today's indictments.
The charges were officially filed on Tuesday, the US attorney's office for D.C. said. "If they are not allowed to protect me in the United States, why do I bring them there with me?" They also violently attacked journalists covering the event, kicking an American cameraman in the chest to prevent him capturing the president's arrival.
A chaotic and bloody scene followed in which the guards, protesters, pro-Erdogan civilians and U.S. law enforcement tangled on the street and in a nearby park.