Rebels shot down a Syrian warplane in the opposition stronghold of Idlib province on Wednesday as Russian-backed government forces closed in on a strategically important town, rebel sources and a war monitor said.
A pilot who ejected from the plane was captured, according to the Syrian Observatory for Human Rights, which reports on the war using a network of sources. Syrian state media made no initial mention of such an incident.
The jihadist Tahrir al-Sham, the most powerful insurgent group in the area, said its fighters had shot down a Sukhoi 22 jet that had taken off from a Syrian air base in Homs province.
The jet was downednear Khan Sheikhoun, a rebel-held town that was hit by a sarin gas attack in2017 and is now being targeted in a Russian-backed government offensive.
Government forces seized new ground from rebels near Khan Sheikhoun on Wednesday, advancing to within a few kilometres (miles) of the town. A rebel commander told Reuters that the town, in opposition hands since 2014, was in "great danger".
Dozens of people were killed in Khan Sheikhoun in 2017 in the poison gas attack that prompted President Donald Trump to order a missile strike against the Syrian air base from where the United States said it had been launched.
An investigationconducted by the United Nations and the Organisation for the Prohibition ofChemical Weapons said the Syrian government was responsible for releasing sarinon the town on April 4, 2017. Damascus denies using such weapons.
Syrian rebels haveshot down government planes on several occasions during the war that spiralledout of the uprising against President Bashar al-Assad in 2011.
Tahrir al-Sham'sstatement did not say how the plane had been shot down. The Syrian Observatoryfor Human Rights said heavy machine guns had been used.
The northwesternIdlib region is part of the last major stronghold of the opposition toPresident Bashar al-Assad.
Assad's side hadstruggled to make any gains in the area in an offensive that got under way inlate April. But since the collapse of a brief ceasefire this month, it hasmanaged to take several significant positions, including the town of al-Habeeton Saturday.
The advance towardsKhan Sheikhoun threatens to encircle the last remaining pocket of rebel-heldterritory in neighbouring Hama province, including the towns of Morek, KafrZeita and Latamneh.
The humanitarianadviser to the U.N. Special Envoy for Syria said the new surge in violence inthe northwest threatened the lives of millions after more than 500 civilianswere killed since late April.
Tahrir al-Sham isthe latest incarnation of the group formerly known as the Nusra Front, whichwas al Qaeda's official wing in the Syrian conflict until they parted ways in2016.
