The pilot managed to eject from the aircraft and parachute down safely, but was then killed by militants on the ground, the MoD stated.
However, the Russian defence ministry said the plane had come down in an area controlled by the al-Qaeda linked jihadist group Jabhat Fateh al-Sham.
A Russian Su-25 warplane was brought down in Syria's Idlib province on Saturday, and the pilot was killed during "a fight" after ejecting by parachute, the TASS news agency quoted Russia's Defense Ministry as saying.
The scenario where a US-backed, US-supplied jihadist group in Syria uses USA weapons to shoot down a Russian plane and then murders the pilot on the ground should be seen as a near-nightmare escalation, drawing the United States and Russia terrifyingly closer to direct conflict.
It happened in a rebel-held area near Idlib in the north of the country.
A video circulating on social media shows a lifeless body of a man, his face stained with blood, as bearded gunmen stand around him.
'The pilot was killed in fighting against terrorists'.
Roles of China, Russia in Latin America 'alarming'
Mr Tillerson noted that China was now the largest trading partner of Chile, Argentina, Brazil and Peru. I understand how important NAFTA is for our economy and that of the continent", Tillerson said.
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Other witnesses said the pilot was taken from the crash site, according to Rami Abdel Rahman, director of the Syrian Observatory for Human Rights, a UK-based monitoring group.
At least five civilians were killed in the bombing of rebel-held Saraqeb city on Saturday, which residents blamed on Russian jets.
Idlib has always been the region where civilians and fighters have gone as they fled rebel-friendly areas under siege by the Syrian regime. Two months later, Turkey shot down a Russian warplane.
A copy of the final statement did not mention the fate of Moscow's ally President Bashar al-Assad.
The Turkish military said two of its soldiers were killed in Syria and a third was killed on the Turkish side of the border in an attack by Syrian Kurdish militiamen.
Around 1,400 delegates attended Tuesday's meeting, as part of a broader push by regime-backer Moscow to consolidate its influence in the Middle East.