Breaking News Emails

Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.
 / Updated 
By Ziad Jaber and NBC News

BEIRUT — A war monitor said on Wednesday the Syrian Army had seized control of the Old City of Aleppo in what would be one of the most important victories of the five-year civil war.

The Syrian Observatory for Human Rights said the army advance on Tuesday and overnight forced insurgents to withdraw from the Old City, including from the area around the historic Umayyad Mosque. The move was a major blow to rebels who have already lost much of the urban stronghold in the last two weeks.

Syria's Reconciliation Minister Ali Haidar said the advance was a "strategic victory" that will prevent foreign intervention and alter the political process, according to Reuters.

"Those who believed in the Syrian triumph, know that [the rebels'] morale is at its lowest and that these collapses that have begun are like domino tiles," he said.

Smoke billowing near the historic citadel during fighting between Syrian regime forces and rebel fighters on Saturday.YOUSSEF KARWASHAN / AFP - Getty Images

A military source confirmed to Reuters on Wednesday that the Syrian army had entered Aleppo's Old City. A Turkey-based official with one of the rebel factions told Reuters government forces had taken part of the Old City, but not all of it.

There was no reason given for the conflicting accounts. However, journalists do not operate freely in the area and NBC News was not able to confirm differing versions of events.

The Syrian army and allied forces' advances — which are being supported by heavy air strikes and shelling — are looking closer than ever to driving rebels out of the besieged eastern sector of the city.

Related: Aleppo Child Back After Twitter Account Went Dark

Restoring full control over Aleppo, Syria's most populous city before the war, would be a major prize for Syrian President Bashar al-Assad.

The war has killed hundreds of thousands of people, made more than half of Syrians homeless and created the world's worst refugee crisis.

Meanwhile on Wednesday, rebels groups inside Aleppo called for a five-day ceasefire so that an estimated 500 severely wounded people could be transported under the supervision of the United Nations.

Speaking in a joint statement, they also asked any civilians who wanted to leave to be allowed safe passage. Although they did not appear to be in a strong position to haggle, the rebels said this would allow all sides of the conflict to "negotiate towards the future of the city."

The statement blamed "the absence of the international community’s role and the humanitarian agencies’ role," and said they would be "fully responsible for whatever the civilians of Aleppo are subjected to."

Reuters and The Associated Press contributed.