Jihadists Wednesday downed a regime plane flying over northwest Syria as it took part in a deadly campaign that has seen loyalists inch forward against their opponents, a monitor said.
An AFP correspondent saw smoke rising in the south of Idlib province above the debris of the plane, with its wing bearing the Syrian flag.
After eight years of civil war in Syria, the Idlib region -- controlled by Syria's former Al-Qaeda affiliate -- is the last major stronghold of opposition to President Bashar al-Assad's regime.
Regime and Russian air strikes, as well as rocket fire, have pounded Idlib for more than three months, killing hundreds and displacing 400,000 people.
Over the past week, pro-Assad fighters have nibbled away at the southern edges of Idlib and on Wednesday they stood just kilometres away from a key jihadist-held town.
The Syrian Observatory for Human Rights said Wednesday's downing of the plane was the first such incident since late April.
"The pilot has been taken prisoner" and is in the hands of the Hayat Tahrir al-Sham (HTS) jihadist group running the Idlib region, Observatory head Rami Abdel Rahman said.
HTS and the correspondent said the Russian-made war plane was downed near the town of Al-Tamanaa.
The crash site lies east of the near-deserted town of Khan Sheikhun, which lies on a key highway coveted by the regime.
The road in question runs through Idlib, connecting government-held Damascus with the northern city of Aleppo, which was retaken by loyalists from rebels in December 2016.
- Rescue worker killed -
"Regime forces are now four kilometres (2.5 miles) from Khan Sheikhun to the west, with nothing between them and it but fields," Abdel Rahman said earlier on Wednesday.
To the east, pro-Assad fighters are battling to control a hill just six kilometres (less than four miles) from the town, he said.
Also on Wednesday, Russian air strikes killed four civilians near the town of Maaret Hurma in the south of Idlib province, according to the Observatory, which relies on sources inside Syria for its information.
They included a paramedic, an ambulance driver, and a rescue worker, it said.
Four other civilians died in regime strikes on the town of Maaret al-Numan.
Clashes on Wednesday killed 16 regime forces, as well as 24 jihadists and seven allied rebels, the Observatory said.
AFP correspondents have reported seeing dozens of families flee fighting over the past few days, heading north in trucks stacked high with belongings.
On the highway not far from the Turkish border on Wednesday, a family was driving north in their pick-up truck.
"We left our sheep, we left our homes, and we fled," said Abu Ahmad, 55, behind the wheel on the road near the town of Sarmada.
Sitting beside him, his wife Umm Ahmad said they had left farmland full of grapes and figs behind near the town of Maaret al-Noman.
- Up the pressure -
A buffer zone deal brokered by Russia and Turkey last year was supposed to protect the Idlib region's three million inhabitants from an all-out regime offensive, but it was never fully implemented.
An alliance led by HTS fighters took full control of the anti-Assad stronghold in May.
Regime and Russian air strikes and shelling since late April have killed more than 820 civilians, according to the Observatory.
It said more than 1,280 jihadist fighters and 1,140 regime forces have died in the same period.
The United Nations says dozens of health centres have been targeted.
Humanitarian workers have warned that any fully-blown ground attack on Idlib would cause one of the worst humanitarian disasters of Syria's war.
The conflict has killed more than 370,000 people and displaced millions at home and abroad since starting with the brutal repression of anti-regime protests in 2011.
Backed by Russia's military since 2015, government forces have taken back large parts of the country from rebels and jihadists.
But Idlib, along with nearby areas controlled by Turkey-backed rebels and a large swathe of the northeast held by Kurds all remain beyond its grasp.
Analyst Nawar Oliver said that, with the ongoing air strikes and ground advances, government forces aimed not only to retake the road running through Idlib, but also pile pressure on HTS and allied rebels.
Regime forces "won't hesitate to bite off or control everything they can," said this expert for the Turkey-based Omran Center for Strategic Studies.
They want to "impose a new reality on the region, the rebels, and ... (the rebels') Turkish ally, and to use it as a tool or weapon in any current or future negotiations," he said.