Rebel offensive to cross into city’s east eases as regime forces fight back, amid UN concern over civilian deaths.

A rebel assault to break the siege of Syria’s Aleppo slowed on Monday amid fierce resistance from regime forces, as the United Nations said it was “appalled” by opposition fire on civilians.

Rebels launched a major assault on Friday, backed by car bombs and salvos of rockets, to break through government lines and reach the 250,000 people besieged in the city’s east.

Aleppo has been hit by some of the worst violence in Syria’s five-year conflict, turning the once-bustling economic hub into a divided and bombed-out symbol of the brutal war.

Since Friday, opposition factions have amassed on Aleppo’s western outskirts in a bid to end the regime’s three-month encirclement of the city’s eastern districts.

While they scored an initial advance, the offensive has since slowed, according to the Syrian Observatory for Human Rights, a Britain-based monitor.

“Since Sunday, the regime has been taking the initiative and the clashes are less intense,” the Observatory head Rami Abdel Rahman said on Monday.

“The only thing that has been accomplished is partial control over Dahiyat al-Assad,” a neighbourhood on Aleppo’s western outskirts that rebels entered on Friday, he said.

Syrian and Russian air strikes were hitting the battlefronts on the city’s edges, but with less intensity than in previous days.

“The momentum of the rebel offensive slowed after failing to take control of the ‘3,000’ apartment block and the military complex,” a pro-government military source said, referring to two built-up areas southwest of Aleppo.

Civilian toll rises

In a new toll on Monday, the Observatory said a total of 61 government troops and their allies were killed in the assault, as well as 72 Syrian rebels.

Heavy rebel rocket fire since Friday has killed 48 civilians, including 17 children, the monitor said.

According to Syrian state news agency SANA, three civilians were killed in rebel fire on Aleppo on Monday.

Al Jazeera was unable to independently verify the death toll.

Syria’s army said in a statement on Monday that al-Nusra Front and what it called other “terrorist” groups had killed 84 people, mostly women and children, in Aleppo during the past three days, adding that the bombardment included chemical weapons.

Al-Nusra Front broke allegiance with al-Qaeda and changed its name to Jabhat Fateh al-Sham in July. It is one of the main rebel groups taking part in the Aleppo offensive.

UN Peace Envoy Staffan de Mistura said the high civilian toll raised deep concern.

In a statement on Sunday, his office said he was “appalled and shocked by the high number of rockets” fired by rebels.