The Russian and US governments blamed each other for a collision between Russian and US armored vehicles in northeastern Syria, in which several US soldiers were injured.
Video of the collision was released by a Russian nationalist website, Rusvesna.su, and then widely retweeted.
The video appears to show a Russian military vehicle in a desert convoy crashing into an American armored car, as a Russian helicopter flies low.
Russia says the United States has prevented a patrol.
News of the incident broke on Wednesday and the Russian Defense Ministry said it had warned the U.S. military it would patrol the area.
“Despite this, in violation of existing agreements, the soldiers of the US armed forces attempted to block the Russian patrol,” said a ministry statement quoted by the Tass news agency.
“In response to this, the Russian military police took the necessary measures to prevent an incident and to continue to fulfill the mission entrusted to them.”
The White House National Security Council (NSC) said a Russian vehicle struck a US mine-resistant all-terrain vehicle, “causing injury to the crew of the vehicle.”
An anonymous US military source told the Politico website that four US soldiers suffered mild concussions.
The United States has around 500 troops in the region – far fewer than before – to help protect it against any new threat from Islamic State (IS) jihadists. The US military assists the Kurdish-led alliance of Syrian Democratic Forces (SDF).
NSC spokesman John Ullyot, as quoted by Politico, said the incident occurred around 10:00 a.m. local time on Wednesday when a routine security patrol encountered Russian troops near Dayrick in the north -est of Syria.
Condemning the Russian military for colliding with an American vehicle, he said the coalition patrol then left the area “to defuse the situation”.
“Dangerous and unprofessional actions like this represent a violation of the deconfliction protocols, committed by the United States and Russia in December 2019,” Mr. Ullyot said.
Russia has provided tremendous firepower, including heavy bombers, to the forces of Syrian President Bashar al-Assad who are fighting various rebel groups, including ISIS.
There have been numerous incidents involving US forces in northeastern Syria. About a week ago, they came under fire from Russia’s Syrian allies.
In February 2018, a large force of Russian mercenaries launched an assault on American positions near a major oil field. They were pushed back and suffered heavy losses.
This last incident is different, however. It is the result of a direct confrontation between the official Russian army and American troops. The Americans claim this is part of a series of incidents. Russia is breaking a variety of local coordination agreements, they say, and essentially harassing US forces.
So why is this happening now? Moscow sees the United States as on its way out in Syria. Last October, President Donald Trump decided to withdraw 1,000 American troops who were operating in support of Kurdish allies, to change their mind, keeping a much smaller force in a smaller area.
But Russia knows that Mr. Trump wants to reduce Washington’s military footprint abroad. Moscow seems to want to show the Americans the door.