Syria's former al-Qaeda affiliate claimed responsibility for the downing of a Russian warplane in northern Syria, apparently using a surface-to-air missile.
The pilot was killed after he ejected and exchanged gunfire with militants on the ground, the Russian Defence Ministry and a monitoring group said.
Hayat Tahrir al-Sham, or HTS, a powerful rebel alliance that publicly split from al-Qaeda last year, said it had used a man-portable anti-aircraft system to shoot down the Su-25 fighter jet as it flew low over the opposition-held town of Saraqeb. That claim was echoed by Russia's Interfax news agency, quoting the Defence Ministry, as well as the Britain-based Syrian Observatory for Human Rights.
The incident could raise tensions between Russia and Turkey, which is monitoring a so-called "de-escalation zone" in the northern province of Idlib as part of an agreement made during Syrian peace talks in the Kazakh capital, Astana.
It also raises questions about the source of the apparent Manpads, a weapon for which Syria's rebels have repeatedly pleaded from their international backers. The US in particular has been strongly opposed, fearing that anti-aircraft weapons could fall into the hands of the country's extremist groups. "The US has never provided Manpad missiles to any group in Syria, and we are deeply concerned that such weapons are being used," State Department spokeswoman Heather Nauert said.
Saraqeb has come under heavy bombardment from Russian and Syrian warplanes in recent days as pro-government forces try to recapture a strategic highway linking Damascus to Aleppo. The White Helmets civil defence group said seven civilians had been killed in at least 25 strikes on largely residential areas, some of them using barrel bombs. In the hours after the Russian jet was downed, Moscow also claimed to have killed more than 30 militants in the area, Interfax reported. The agency quoted the Defence Ministry as saying it used "precision-guided weapons" to carry out the strike, but without giving details.
The use of Manpads in a province where Turkish forces are nominally present could also anger Russia. The two countries have improved ties and cooperated in Syria in recent months, but relations hit an all-time low in 2015, when Turkey, a longtime supporter of the country's rebels, also shot down a Russian warplane inside Syria.
Turkey set up observation points in Idlib last year, ostensibly to monitor the fighting between the rebels and government forces, but it has also been accused of fostering closer ties with HTS.
Moscow entered Syria's civil war in 2015 on the side of President Bashar al-Assad. And its intervention turned the tide of the brutal war, allowing Syria's Government to recapture Aleppo from the rebels and beat back militants in other parts of the country. But Idlib remains under militant control, and HTS exercises significant influence even over areas it does not formally hold.
Manpad has deadly impact
• Rebels have shot down Syrian regime jets in the past but this marks the first time a Russian warplane was brought down by opposition ground fire.
• In August 2016, a Russian military helicopter was shot down over Syria and five people were killed.
• Orient News, an opposition media outlet, claimed the jet was shot down with an Igla anti-aircraft missile, a shoulder-fired weapon which can be carried by a single person.
• The rebels have been known to use such weapons, known as man-portable air-defence systems (Manpads) in the past, but it is not clear who would have supplied them.
• Western countries have long been wary of supplying rebels with Manpads for fear they would fall into jihadist hands and could be used against Western civilian or military aircraft.
• Michael Horowitz, a senior analyst at the Le Beck geopolitical consultancy, said the shoot down was not "a game changer" as the Su-25 flies low in support of ground troops and is therefore vulnerable to anti-aircraft fire.
- Addtional reporting: Telegraph