Russian fighter jets accused of conducting dangerous manoeuvres for second day near US military drones over Syria.

Russian fighter jets have again flown dangerously close to several US MQ-9 Reaper drones operating over Syria – the second such incident of harassment in 24 hours – setting off flares and forcing Washington’s unmanned aerial vehicles to take evasive manoeuvres, the United States air force said.

The protest from the US air forces came as the French military said that two of its fighter jets on patrol over the Iraq-Syria border area were forced to manoeuvre “to control the risk of accident” involving a Russian Sukhoi SU-35 warplane on Thursday.

The Russian aircraft had engaged in “non-professional interaction” with two of France’s Rafale planes deployed to the region as part of “Operation Chammal”, which seeks to contain the ISIL (ISIS) group in Iraq and Syria, the French military said.

Two separate incidents on Wednesday and Thursday involving Russian warplanes and US Reaper drones were captured on video, the US said.

“The events represent a new level of unprofessional and unsafe action by Russian air forces operating in Syria,” the US military said.

“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,” Lieutenant General Alexus Grynkewich, head of US Air Forces Central Command, said in a statement.

In the first incident, which took place about 10:40am (07:40 GMT) local time on Wednesday in northwest Syria, Russian Sukhoi SU-35 fighters closed in on a Reaper drone, and one of the Russian pilots moved their aircraft in front of the US aerial vehicles and engaged the SU-35’s afterburner, which greatly increases its speed and air pressure.

The jet blast from the afterburner could have potentially damaged the Reaper’s electronics, and Grynkewich said it reduced the drone operator’s ability to safely operate the aircraft.

Later, a number of so-called parachute flares released by the Russian planes moved into the drone’s flight path. The flares are attached to parachutes.

In the second incident, which took place over northwest Syria at approximately 9:30am (06:30 GMT) on Thursday local time, “Russian aircraft dropped flares in front of the drones and flew dangerously close, endangering the safety of all aircraft involved,” Grynkewich said.

The Reaper drones involved in the incidents were not armed with weapons and are commonly used for reconnaissance missions.

Earlier this year, a diplomatic dispute erupted briefly when the US claimed that Russian jets were responsible for the downing of a Reaper drone, valued at more than $30m and packed with sensitive US spying technology, operating over the Black Sea.

Moscow denied its warplanes were responsible for the drone crashing into the sea in March but video footage released by the US military showed the Russian planes engaged in manoeuvres to hamper the drone’s flight path.

US officials said the Russian jets flew around and in front of the Reaper drone several times for 30 to 40 minutes, and then one “struck the propeller” of the drone, “causing US forces to have to bring the MQ-9 down in international waters”.

The US said the drone was operating in international airspace, reportedly west of Ukraine’s Crimea over the Black Sea. The Russian defence ministry said the drone had intruded into an area that was declared off-limits by Russian authorities.

Of the latest incidents, US Army General Erik Kurilla, head of US Central Command, said in a statement that Russia’s violation of ongoing efforts to clear the airspace over Syria “increases the risk of escalation or miscalculation”.

About 900 US forces are deployed to Syria to work with the Kurdish-led Syrian Democratic Forces battling ISIL fighters.

In April, Russian forces operating in Syria accused the US military of engaging in “provocative actions” on the ground.

Russia together with Turkey carries out joint patrols in northern Syria and has agreed on special zones where the US-led coalition can operate in its fight against ISIL.