Jihadists and their Turkish-backed allies reached Syria's second city of Aleppo as they pressed a lightning offensive against forces of the Iranian- and Russian-backed government.
The fighting is some of the deadliest in years, with 277 people killed, according to the Syrian Observatory for Human Rights. Most of the dead are combatants although the toll also includes 28 civilians, most killed by Russian air strikes.
The offensive began on Wednesday, the same day that a fragile ceasefire took effect in neighbouring Lebanon between Israel and Iran-backed militant group Hezbollah.
The jihadists and their allies had wrested control of more than 50 towns and villages in the north, according to the Britain-based Observatory, in the government's biggest loss of territory in years.
They then entered western districts of Aleppo, a city of some two million people that was Syria's pre-war manufacturing hub.
The fighters "advanced without any significant pushback from regime forces", Observatory director Rami Abdel Rahman said, adding that they had taken control of five neighbourhoods of the city.
An army statement said troops had repelled the assault on the city and retaken some positions.
Russian air strikes
Syrian and Russian warplanes launched intense air strikes on the rebel enclave around Idlib, where the jihadists are based, carrying out 23 raids, according to the Observatory.
The Russian military said it was bombing "extremist" forces.
"The Russian air force is carrying out rocket-bomb attacks on... control points, warehouses and artillery positions of terrorists," a defence ministry spokesperson told Russian news agencies.
Turkey demanded a halt to the bombardment. "The recent clashes have resulted in an undesirable escalation of tensions in the region," a foreign ministry statement said.
The Idlib area has been subject to a Turkish- and Russian-brokered truce since 2020. The ceasefire has been repeatedly violated but had largely held.
The United Nations Office for the Coordination of Humanitarian Affairs said "more than 14,000 people -- nearly half are children -- have been displaced" by the violence.
Yesterday, the jihadists and their allies cut the highway linking Aleppo to the capital Damascus, some 300 kilometres south, the Observatory said.
International players
Russia spokesman Dmitry Peskov on Friday described the situation in Aleppo as "an infringement on the sovereignty of Syria".
He expressed support for "the government of Syria to quickly restore order in this district".
Iranian Foreign Minister Abbas Araghchi pledged "continued support for the government, nation and army of Syria," in a phone call with his Syrian counterpart Bassam al-Sabbagh, according to a statement.
Analyst Nick Heras, of the New Lines Institute for Strategy and Policy, said the fighters were "trying to preempt the possibility of a Syrian military campaign in the region of Aleppo".
According to Mr Heras, the Syrian government and its ally Russia had been preparing for such an offensive.
As well as Russia, Syrian President Bashar al-Assad has been propped up by Iran and allied militant groups, including Lebanon's Hezbollah.
Iran-backed militias have a heavy presence in the Aleppo region after providing crucial ground support to the army in its recapture of rebel-held areas of the city in 2016.
Mr Heras said anti-government forces are "in a better position to take and seize villages than Russian-backed Syrian government forces, while the Iranians are focused on Lebanon".
