The Turkish embassy released a statement late Wednesday that contradicted United States officials and video evidence and blamed the demonstrators, who, it said, had been “aggressively provoking Turkish-American citizens who had peacefully assembled to greet the president.” The president’s supporters and security forces were reacting in self-defense, the statement said.

The altercation, which played out in broad daylight and ricocheted across social media on Tuesday, puts the United States in an uncomfortable position as it must navigate investigating and potentially charging the security personnel and other Erdogan supporters involved in the attack, who could potentially claim diplomatic immunity.

Chief Newsham demurred when asked whether members of Mr. Erdogan’s security team were involved in the attack, but the State Department later acknowledged their presence. Mr. Erdogan and his security guards have since left the country. It was unclear if embassy staff had also been involved.

Chief Newsham said an investigation was continuing, adding that the authorities were reviewing video from the scene and had a good sense of who was involved. He said that some members of the pro-Erdogan group were carrying firearms, which made it more difficult for the police to contain the scene.

“We intend to assure that there is accountability for anyone involved in this assault,” Chief Newsham said. “Yesterday we witnessed what appeared to be a brutal attack on peaceful protests.”

The Secret Service, which provides protection for visiting dignitaries, said in a statement it would work with the police and the State Department “to aggressively pursue accountability for those involved in yesterday’s protests.”