A dramatic video shows Russian fighter jets "harassing" US drones over Syria as they carry out missions against Islamic State militants, an official has said.
A US Air Force general slammed the incident on Wednesday as "unsafe and unprofessional behaviour" and said it "threaten[s] the safety of both U.S. and Russian forces,"
He called on Russia to stop the "reckless behaviour" in Syria where US still has 900 troops.
Sensors and cameras on board the three MQ-9 Reaper drones captured the Russian fighter jets flying very close to the unmanned aerial vehicles.
The Russian jets also dropped multiple parachute flares in the drones' path.
Lieutenant General Alex Grynkewich, the commander of the Ninth Air Force and the combined forces air component commander for US Central Command, said in a statement: "These events represent another example of unprofessional and unsafe actions by Russian air forces."
The US have accused Russian forces of carrying out provocative flights over eastern Syria.
In mid-June, CENTCOM announced that it was deploying F-22 Raptors to deter flights above American military bases in the region.
This is just the latest in a number of encounters with a similar video in March showing a Russian fighter jet harassing a drone leading to a collision.
"Against established norms and protocols, the Russian jets dropped multiple parachute flares in front of the drones, forcing our aircraft to conduct evasive manoeuvres," Lt. Gen. Grynkewich said.
"Additionally, one Russian pilot positioned their aircraft in front of an MQ-9 and engaged afterburner, thereby reducing the operator’s ability to safely operate the aircraft," he added.
"We urge Russian forces in Syria to cease this reckless behaviour and adhere to the standards of behaviour expected of a professional air force so we can resume our focus on the enduring defeat of ISIS.”
"Russian Forces' unsafe and unprofessional behaviour is not what we expect from a professional air force. Their regular violation of agreed upon airspace deconfliction measures increases the risk of escalation or miscalculation," General Michael "Erik" Kurilla, head of CENTCOM, said then. "Alongside our partners and allies, we are committed to improving the security and stability in the region."
Defence officials have complained there have been dozens of incidents where Russian jets have flown over US bases without taking proper precautions.
In March the US military launched devastating air strikes after a drone killed an American contractor and injured five troops.
The Pentagon said a suspected Iranian drone struck a facility in northeast Syria which led to American forces to retaliate with “precision airstrikes” in Syria.
US Defence Secretary Lloyd Austin said in a statement that the American intelligence community had determined the drone was of Iranian origin.
He said: “The airstrikes were conducted in response to today’s attack as well as a series of recent attacks against coalition forces in Syria” by groups affiliated with the Revolutionary Guard."
