The Russian and US governments have blamed each other for a collision between Russian and US armoured vehicles in north-eastern Syria in which several US troops were injured.
Video of the collision was broadcast by a Russian nationalist website, Rusvesna.su, then widely retweeted.
The video appears to show a Russian military vehicle in a desert convoy ramming a US armoured car, as a Russian helicopter flies low overhead. Russia says the US obstructed a patrol.
News of the incident broke on Wednesday. The Russian defence ministry said it had given the US military prior warning that it would be patrolling in the area.
“Despite that, in violation of existing agreements, the US armed forces soldiers tried to block the Russian patrol,” said a ministry statement quoted by Tass news agency.
“In response to that, the Russian military police took necessary measures to prevent an incident and to carry on fulfilling the mission they had been given.
“The White House National Security Council (NSC) said a Russian vehicle had struck a US mine-resistant all-terrain vehicle, “causing injuries to the vehicle’s crew”.
An unnamed US military source told the Politico website that four US soldiers had suffered mild concussion.