Officers opened fire in west London on Saturday morning while responding to reports of a car collision, the Metropolitan Police has said.
The Ukrainian embassy said its ambassador’s car was “deliberately rammed” as it sat parked outside the building in Holland Park.
When officers arrived on the scene, a vehicle was “driven at them”, the Met added.
Officers used firearms and a Taser before arresting a man in his 40s.
Police said the uninjured man was “taken to a central London hospital as a precaution”.
They added that the situation was neither ongoing nor being treated as terror-related.
Describing the events of Saturday morning, the Ukrainian embassy said that after seeing the ambassador’s car being targeted, the police were called and officers “blocked up” the attacker’s vehicle.
“Nevertheless, despite the police actions, the attacker hit the ambassador’s car again,” the embassy added.
“In response, the police were forced to open fire on the perpetrator’s vehicle.”
The embassy said none of its staff had been injured and that police were now investigating “the suspect’s identity and motive for the attack”.
A woman who works at a nearby shop told the Press Association she heard shots fired twice between 10:00 GMT and 11:00.
The woman, who did not wish to be named, said officers arrived “very quick”, adding: “I saw many police cars coming.”
Ch Supt Andy Walker, from the Met’s specialist firearms command, added: “As is standard procedure, an investigation is now ongoing into the discharge of a police firearm during this incident.
“While this takes place, I would like to pay tribute to the officers involved this morning who responded swiftly to this incident and put themselves in harm’s way, as they do every day, to keep the people of London safe.”