Jihadists and their Turkish-backed allies reached Syria's second city of Aleppo on Friday, 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 255 people killed, according to the Syrian Observatory for Human Rights. Most of the dead have been combatants but the toll also includes 24 civilians, most killed in 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.
On Friday, 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.
"Hayat Tahrir al-Sham (HTS) and allied factions... were able to enter the outskirts of the Al-Hamdaniya and New Aleppo neighbourhoods... after carrying out twin suicide attacks with two booby-trapped cars," the war monitor said.
HTS, a jihadist alliance led by Al-Qaeda's former Syria branch, shelled a student residence in the city, killing four civilians, state media reported.
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.
Army reinforcements have arrived in Aleppo, a Syrian security official told AFP, requesting anonymity to discuss sensitive matters. An army statement said troops had repelled the assault on the city and retaken some positions.
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.
On Thursday, the jihadists and their allies cut the highway linking Aleppo to the capital Damascus, some 300km south, the Observatory said.
