Tens of thousands of people have fled their homes in Aleppo after the Syrian army declared two Kurdish neighbourhoods “closed military zones” amid a second day of clashes with the Kurdish-led Syrian Democratic Forces (SDF).

The directorate for social affairs said on Wednesday night that more than 45,000 people had been displaced from the city due to the fighting, most of them heading northwest towards the enclave of Afrin.

Syria’s government opened humanitarian corridors for civilians to flee flashpoint areas, ferrying them out on city buses.

“We fled the clashes and we don’t know where to go … Fourteen years of war, I think that’s enough,” Ahmed, a 38-year-old man who only gave his first name, told the AFP news agency while carrying his son on his back.

Another displaced resident, 41-year-old Ammar Raji, said he and his family were “forced to leave because of the difficult circumstances”.

“I have six children, including two young ones … I am worried we will not return,” Raji said.

The Syrian Army Operations Command had said earlier in the day that all SDF military positions in Aleppo were legitimate targets as fighting between government forces and the Kurdish-led SDF continued after violence flared a day earlier.

The clashes, which killed nine people on Tuesday, according to officials, are the fiercest fighting since the two sides failed to implement a March deal to integrate the SDF into Syria’s new state institutions.

The Syrian army said the Sheikh Maqsoud and Ashrafieh neighbourhoods of Aleppo would be considered “closed military zones” as of 3pm local time (12:00 GMT) on Wednesday, urging residents to leave through two humanitarian corridors.

All SDF “military sites” in the two neighbourhoods “are a legitimate military target … following the organisation’s major escalation towards the neighbourhoods of Aleppo city and its perpetration of numerous massacres against civilians”, the Army Operations Authority said in a statement.

The SDF acknowledged a large deployment of Syrian army vehicles near the areas, labelling it a “dangerous indicator that warns of escalation and the possibility of a major war”.

Reporting from Aleppo on Wednesday, Al Jazeera’s Resul Serdar said tens of thousands of people were seen gathering their belongings and leaving the neighbourhoods, but many remained trapped amid the fighting.

“And once the clock hit 3pm … we have seen things rapidly escalate: the artillery shelling, the rocket firing, the gunfire – and with drones being involved,” Serdar said.

“There are still thousands of people trapped in Sheikh Maqsoud and Ashrafieh, and the government forces are saying that the SDF is still shelling residential areas,” he added.

“The situation here is extremely tense. Since yesterday, the government is building up its military positions here. More and more ammunition is arriving, heavy army vehicles are arriving, and thousands of troops are constantly going into Ashrafieh.”

Sectarian tensions

Both sides have blamed the other for triggering the violence, which broke out after talks this week between government officials and the main SDF commander stalled with “no tangible results” achieved, according to state media.

The incorporation of the SDF, which controls large swaths of territory in Syria’s north and northeast, into state institutions has remained a subject of consternation since President Ahmed al-Sharaa took office a year ago.

The deal reached in March, in which the SDF agreed for “all civil and military institutions in northeastern Syria” to be merged into “the Syrian state, including border crossings, the airport, and oil and gas fields”, has yet to be carried out.

Muhanad Seloom, an assistant professor in critical security studies at the Doha Institute for Graduate Studies, told Al Jazeera that the fighting in Aleppo signals that the “honeymoon period” following the fall of longtime leader Bashar al-Assad in December 2024 may be over.

“What we are looking at is a race between integration and disintegration,” said Seloom, referring to Damascus’s struggle to bring minority communities into national institutions, and the danger it poses to the fragile Syrian state.

Al-Sharaa’s efforts to amalgamate power and quell sectarian tensions among the numerous groups across Syria after al-Assad’s fall have not been helped by Israel.

Prime Minister Benjamin Netanyahu’s government has carried out persistent raids and bombardments in a bid to demilitarise southern Syrian regions bordering Israel.

Over the past year, Israel has launched more than 600 air, drone and artillery attacks across Syria, averaging nearly two a day, according to a tally by the Armed Conflict Location and Event Data Project.

Marie Forestier, a nonresident senior fellow for the Atlantic Council’s Syria Project, told Al Jazeera that the distance between Syrian, Israeli and US goals is “very difficult”, especially given that “Israel is doing everything to destabilise Syria”.