Syria's army said its operation in a Kurdish neighborhood of Aleppo was nearing completion early Saturday and urged fighters from the minority to surrender themselves and their weapons.
Government forces began striking the Sheikh Maqsud district overnight after the Kurdish fighters defied a deadline to withdraw during a temporary ceasefire.
A military source told the official SANA news agency that the combing operation in Sheikh Maqsud was "more than 90 percent" complete, and that "a number of SDF members" had been arrested.
In a statement posted by the Ministry of Defense, Syria's army said "the only remaining option for the armed elements in the Sheikh Maqsud area of Aleppo is to surrender themselves and their weapons immediately".
The violence in Syria's second city erupted after efforts to integrate the Kurds' de facto autonomous administration and military into the country's new government stalled.
Since the start of the fighting on Tuesday, at least 21 civilians have been killed, according to figures from both sides, and tens of thousands have fled Aleppo.
The clashes, some of the most intense since Syria's new authorities took power, present yet another challenge as the country struggles to reunify after ousting longtime ruler Bashar al-Assad in December 2024.
Both sides blame the other for starting the violence.
Early Friday, Syrian authorities announced a six-hour window for the Kurdish fighters to leave, but they instead refused to "surrender" and vowed to defend their districts.
In response, Syria's army warned it would renew strikes on military targets in Sheikh Maqsud and urged civilians to get out ahead of the district's takeover by security forces.
An AFP correspondent saw residents laden with belongings fleeing before the two-hour humanitarian corridor closed.
Kurdish forces reported coming under artillery and drone attacks and claimed in a post on social media to be mounting a "fierce and ongoing resistance".
The army said three soldiers had been killed by Kurdish forces, while state television accused them of launching drones on residential areas of Aleppo.
A flight suspension at Aleppo airport was extended until late Saturday.
The SDF controls swathes of Syria's oil-rich north and northeast, and was key to the defeat of the ISIS group in 2019.
But Ankara views its main component as an extension of the Kurdistan Workers' Party (PKK), which agreed last year to end its four-decade armed struggle against Türkiye.
Elham Ahmad, a senior official in the Kurdish administration in Syria's northeast, accused Syria's authorities of "choosing the path of war" by attacking Kurdish districts and of "seeking to put an end to the agreements that have been reached".
"We are committed to them and we are seeking to implement them," she told AFP.
The March integration agreement was meant to be implemented last year, but differences, including Kurdish demands for decentralized rule, have stymied progress.
Ahmad said that "the United States is playing a mediating role... we hope they will apply pressure to reach an agreement".
A diplomatic source told AFP that US envoy Tom Barrack was headed to Damascus.
Türkiye, which shares a 900-kilometer (550-mile) border with Syria, has launched successive offensives to push Kurdish forces from the frontier.
Syrian President Ahmed al-Sharaa discussed the situation in a call with Turkish leader Recep Tayyip Erdogan and said he was determined to "end the illegal armed presence" in the city, a Syrian presidency statement said.
UN spokesperson Stephane Dujarric expressed alarm over the impact of the fighting on civilians and called on all parties "to swiftly return to negotiations to ensure the full implementation of the 10 March agreement".
Nanar Hawach, senior Syria analyst at the International Crisis Group, said the renewed clashes cast doubt on the government's ability to gain the trust of minority factions and sow the country back together after 14 years of civil war.
"If the fighting escalates, international actors will wonder about Damascus's capacity to govern Syria's heterogeneous society," he added.
Syria's authorities have committed to protecting minorities, but sectarian bloodshed rocked the Alawite and Druze communities last year.
