Turkish authorities said they had detained 15 members of a nationalist youth organisation in connection with the assault of two US Marines stationed in a port city in western Turkey on Monday.
The Marines, members of the 24th Marine Expeditionary Unit, were off their ship and wearing plain clothes at the time of the attack in Izmir, Turkey, Cmdr. Timothy Gorman, a spokesperson for the US 6th Fleet, told CBS News. They were taken to a hospital for evaluation as a precaution, he said.
The Marines have since returned to the ship and are safe, officials said.
"Local Izmir police and the Naval Criminal Investigative Service are cooperating in an investigation of the incident," Gorman told CBS. "No Marines have been detained by authorities and those involved are cooperating with investigators."
The Izmir governor's office said in a statement on social media that members of the Turkish Youth Union were detained after the attack. The nationalist group is affiliated with the Patriotic Party, a nationalist group that does not hold any seats in Turkey's parliament, and has anti-American views, according to The Associated Press.
The US Embassy said in a statement on social media that the service members who had been assaulted were safe and aboard their amphibious assault ship, the USS Wasp.
Video posted on social media and verified by the news agency Storyful appeared to show the attack on the Marines. The footage shows a group of young men crowding around a man, restraining him and attempting to put a sack over his head, while another man tries to intervene and push members of the group away.
People could be heard chanting "Yankee go home" in English in the footage.
In 2014, members of the nationalist youth group were arrested in connection with the assaults of three visiting American sailors in Istanbul. Members of the group used similar tactics at the time -- a large group descending on a few servicemen on leave and pulling white sacks over their heads -- and uttered similar chants, including "Yankee go home!" and "Down with US imperialism!"
The USS Wasp arrived in Izmir on Sunday for a regularly scheduled port visit after a joint training exercise with Turkey in the Mediterranean, according to the Department of Defense. The vessel was sent to the region as a part of broader plan by the US Navy to deter further conflict in the Middle East.