Syrian government troops advanced gradually against rebels inside ravaged second city Aleppo on Friday, as the UN Security Council prepared to hold an emergency meeting to discuss the violence.
The assault on rebel-held districts of the divided city has raised international concern, with UN envoy Staffan de Mistura warning east Aleppo could be "totally destroyed" by year's end.
Fierce fighting rocked several districts of the city, which has been divided between government control in the west and rebel control in the east since 2012.
The Syrian Observatory for Human Rights said government forces captured a hilltop in the Sheikh Saeed district in the south of the city, but the rebels retook other parts of the neighbourhood previously captured by the regime.
The Britain-based monitoring group also reported clashes in the Salaheddin, Bustan al-Basha and Suleiman al-Halabi neighbourhoods on the city's front line.
Once Syria's economic powerhouse, Aleppo has been ravaged by the war, which has killed more than 300,000 people since it began with anti-government protests in March 2011.
More than 250,000 people remain in the east of the city, which has been under near-continuous siege since mid-July and has been pounded relentlessly since the government launched its offensive on September 22.
The rebels have responded by intensifying their rocket fire on west Aleppo, where four people were killed in the Midan neighbourhood on Friday, state television reported.
On Thursday, rebel fire killed at least 11 people in the Al-Jamaliyeh neighbourhood, the Observatory said.
The army said earlier this week that it would rein in its bombardment of the east, and the Observatory said there had been a reduction of the bombing that has killed hundreds and destroyed the largest hospital in the rebel-held sector.
But it has pressed on with its ground offensive, with President Bashar al-Assad saying his forces had "no option" but to expel rebels from the city unless they agreed a deal with the government.
In an interview with Danish broadcaster TV2 aired on Thursday, Assad said Aleppo's "best option" would be a reconciliation deal like those the government has negotiated with rebels elsewhere.
Opposition forces say those deals have been forced upon them by a government strategy of "surrender or starve."
Assad said that without an agreement, he would "continue the fight with the rebels till they leave Aleppo... There's no other option."
State television reported on Friday that people were leaving east Aleppo through humanitarian corridors but gave no further details and showed no images.
An AFP correspondent said he saw no sign of people leaving, and residents have previously said they feared entering government-controlled territory.
The assault on Aleppo, which began after the collapse of a truce deal negotiated by Russia and the United States, has sparked international condemnation.
On Thursday, UN Syria envoy Staffan de Mistura warned of the operation's consequences.
"In maximum two months, two-and-a-half months, the city of eastern Aleppo may be totally destroyed," he told reporters.
He urged Islamist militants of the former Al-Nusra Front -- now known as Fateh al-Sham Front after splitting with Al-Qaeda -- to leave the city under a deal to halt the government's assault.
"If you decide to leave with dignity... I am personally ready to physically accompany you," he said.
The Security Council is to hold an emergency meeting later Friday at the request of Russia to receive a briefing from de Mistura.
Council members are also discussing a French-drafted resolution calling for a ceasefire in Aleppo.
After holding talks in Moscow on the proposal, French Foreign Minister Jean-Marc Ayrault is to visit Washington later on Friday to discuss the text, which also calls for a halt to all flights over the city.
France's UN ambassador Francois Delattre said Thursday "we have a strong determination to go to a vote" on the draft.