Video has emerged showing Turkish President Recep Tayyip Erdogan watching as his bodyguards violently attacked protesters in Washington DC.
Police condemned the incident as "a brutal attack" and US senator John McCain is calling for Turkey's ambassador to the US to be thrown "the hell out of the United States" over it.
The latest video is taken outside the ambassador's home, where Mr Erdogan sits in a car after his meeting with Mr Trump.
Turkey's President appears to issue a command to an aide, who then talks to another staff member who - along with several other men in black suits, including some identified as Mr Erdogan's bodyguards - charge protesters and brawling breaks out.
According to Turkish state news outlet Anadolu, US police refused to obey "Turkish demands to intervene" in the peaceful protest, so Mr Erdogan's men moved in.
Some of the Turkish guards were detained after the violence and had their guns confiscated, but they were promptly released due to their diplomatic status, according to a congressional aide briefed on the US State Department's investigation
Investigators are said to be now paying particular attention to two members of the Turkish security detail who assaulted US Diplomatic Security officers assigned to protect the visiting delegation.