US drone strike kills Islamic State group leader in Syria

US drone strike killed an Islamic State group leader in Syria hours after the same MQ-9 Reaper drones were harassed by Russian military jets over the western part of the country, according to the Defence Department.

Three Reapers had been flying overhead searching for the militant on Friday, a US defence official said, when they were harassed for about two hours by Russian aircraft.

Shortly after that, the drones struck and killed Usamah al-Muhajir, who was riding a motorcycle in the Aleppo region, said the official, who was not authorised to publicly discuss the matter and spoke on condition of anonymity to describe details of the military operation.

The official said al-Muhajir was in northwest Syria at the time of the strike, but that he usually operated in the east.

In a statement Sunday, US Central Command said there are no indications any civilians were killed in the strike.

The military was assessing reports a civilian may have been injured.

Friday was the third day in a row that US officials complained that Russian fighter jets in the region had conducted unsafe and harassing flights around American drones.

The first friction occurred Wednesday morning when Russian military aircraft engaged in unsafe and unprofessional behaviour as three American MQ-9 drones were conducting a mission against IS, the US military said. 

Col Michael Andrews, Air Forces Central Command spokesman, said the Thursday incident lasted almost an hour and included close fly-bys, by one SU-34 and one SU-35 and that they deployed flares directly into the MQ-9.

US officials said the drones were unarmed in the earlier flights, but were carrying weapons on Friday, as they were hunting al-Muhajir.