Local news reports said Erdogan supporters and security guards clashed with Kurdish and Armenian protesters who accuse him of rights abuses.
(Warning: This video gets a little bloody.)
Erdogan's bodyguards beat up Kurdish protesters in D.C. Just imagine what we are going through back in Turkey. https://t.co/4UhOfS27WJ— Mahir Zeynalov (@MahirZeynalov) May 17, 2017
Erdogan met at the White House with US President Donald Trump for a visit that aimed to improve strained ties.
After Erdogan left the White House, tensions over the Kurdish issue spilled onto the streets of Washington.
The Turkish president stopped by the ambassador's residence in the upscale Sheridan Circle neighborhood, where protests prompted city officials to shut down nearby streets, snarling traffic.
Police managed to keep the rival groups apart at first, but eventually were outmuscled and outmaneuvered.
Erdogan's security detail reportedly attacked protesters carrying the flag of the Kurdish PYD party outside the ambassador's residence.
The government of Turkey believes that the Kurdish Peoples' Protection Units (YPG) in Syria are the Syrian arm of the PKK, which has waged a deadly insurgency inside Turkey since 1984.
Videos from Tuesday's protests in Washington, some of which were posted on the internet, showed people from both sides shouting and being punched — with each side accusing the other of being the aggressors.
"We weren't doing anything wrong," a pro-Erdogan demonstrator, Mustafa Dikilitas, told ABC television. "We just celebrated our president."
"One of the YPG supporters ran across, picked up a megaphone, and hit a Turkish citizen with it," said another pro-Erdogan demonstrator, Busra Eren, referring to the Kurdish militia group.
Demonstrators on the other side, meanwhile, blamed Erdogan's partisans for the violence.
"All of the sudden they just ran towards us," Yazidi Kurd demonstrator Lucy Usoyan told ABC, adding that she was attacked by one of the pro-Erdogan supporters.
"Someone was beating me in the head nonstop, and I thought, 'Okay, I'm on the ground already, what is the purpose to beat me?'"
Washington police eventually sent reinforcements and restored order, but emergency services said nine people were taken to the hospital, one of them in critical condition.