Syrian men displaced from east Aleppo last month wait at a security checkpoint on Sunday to be able to return to their homes in the city’s Hanano district. ( Hassan Ammar /Associated Press)

The Syrian army on Sunday ordered rebels in Aleppo to leave the city or face “inevitable death,” as airstrikes on neighboring Idlib province killed at least 50 people, including several children.

Aleppo shook from the sound of explosions throughout the day as pro-government forces, including fighters dispatched from Lebanon, Iraq and Iran, pounded the city’s opposition neighborhoods in the east.

Rebel defenses have buckled after months of siege and waves of devastating airstrikes, and the opposition could soon be driven from Syria’s largest city.

It would mark their biggest defeat since 2011, when a government crackdown against dissent sparked a civil war. Rebels swept into Aleppo in 2012. The government’s fortunes changed after the Russian air force intervened in September 2015, allowing the government to begin to reconquer it.

Brig. Gen. Samir Suleiman, an army spokesman, said that the army has retaken more than half the neighborhoods in eastern Aleppo and that special forces would lead the battle in the narrow streets of the city’s historic district.

On Sunday, government forces captured large swaths of the Qaterji, Maysar and Karm al-Turab neighborhoods, bringing their eastern flank to within less than half a mile of the citadel that anchors the center of the city. The citadel has remained under government control throughout the conflict.

The United Nations estimates that more than 31,000 people have fled their homes since pro-government forces began advancing inside eastern Aleppo one week ago.

Russian or government jets, meanwhile, were thought to be behind raids on Idlib province on Sunday, including two airstrikes that hit rural markets and killed dozens, activists said.

The Syrian Civil Defense first responder group said 52 civilians were killed in raids across the province.

“The fear was clear on everyone’s face. There were limbs and bodies all over the ground,” said Ahmad al-Sheikho of the Civil Defense, who said he arrived at the Maarat al-Numan marketplace 10 minutes after it was struck.

The market at Kafranbel, a village seven miles away, was bombed a few hours earlier.