Civilians despair as army advances in rebel Aleppo

The US military meanwhile announced its first combat loss in Syria, saying a service member had been killed by a bomb during an offensive against the Islamic State group.

Ten days into the Syrian government's renewed bid to recapture all of battered second city Aleppo, regime bombardment has killed nearly 190 civilians and left residents desperate for respite.

The regime is hoping to score its most important victory yet of the five-year civil war, dealing a potentially decisive blow to the rebels by recapturing eastern neighbourhoods they overran in 2012.

Civilians in the east have been under siege by the army since July, with food and fuel supplies dwindling and international aid completely exhausted.

On Thursday alone, 32 civilians were killed in air strikes and artillery fire on eastern neighbourhoods, among them five children, the Syrian Observatory for Human Rights said.

"I'm terrified by the army's advance and the increasing bombardment," said Abu Raed, a father-of-four living in Fardos neighbourhood.

"There's no safe place for me and my family."

Rescuers pull boy from rubble

The Observatory said the army now controlled more than 60 percent of the strategic Masaken Hanano district and was pushing on.

The advances have been accompanied by relentless air and artillery bombardment, with medical staff in the east accusing the army of dropping barrel bombs filled with chlorine gas.

Damascus and its ally Moscow have repeatedly denied any illegal, military use of the chemical.

Retaliatory rocket fire by the rebels has killed at least 18 civilians in the government-held west, 10 of them children, according to the Observatory.

On Thursday night, rescue workers in several parts of the east battled to extricate civilians trapped under the rubble of bombed buildings.

In Bab al-Nayrab, an AFP cameraman saw rescuers battle for more than an hour to pull out a seriously wounded boy.

The lower part of his body was trapped and the back of his head badly gashed.

He cried out "father, father," as the rescuers used pickaxes to break up the concrete surrounding him.

The desperate conditions have prompted some civilians to flee.

In recent days, five families have crossed to Sheikh Maqsud, a Kurdish-controlled enclave between the government-held west and rebel-held east, the Observatory said.

Damascus says residents and surrendering fighters are free to leave, and accuses the rebels of preventing civilians from doing so and using them as "human shields."

'Unbearable circumstances'

On the ground, residents expressed despair.

"Living under these circumstances is unbearable," said 43-year-old Mohammed Haj Hussein, in Tariq al-Bab district.

"There's no work, there's no food, and the bombing is incessant... I want to get out of here by any means possible."

In Bab al-Nayrab district, Abu Hussein said: "I don't know what the UN is waiting for. Why don't they at least evacuate the children and women?"

The UN says it has a plan to deliver aid to Aleppo and evacuate the sick and wounded, which rebel factions have approved.

But Damascus has yet to agree, and additional guarantees are needed from Moscow, UN officials say.

On Thursday, the head of the UN-backed humanitarian taskforce for Syria, Jan Egeland, warned there was no plan B to help civilians in east Aleppo.

"In many ways plan B is that people starve, and can we allow that to happen? No we cannot," he said.

Further east, in Raqa province, where a US-backed alliance of Kurdish and Arab fighters is battling IS, Washington suffered its first combat loss in Syria, the US-led coalition announced.

It said the service member died on Thursday from wounds caused by an improvised bomb near the town of Ayn Issa.

US special forces are on the ground in the area supporting an offensive to retake the city of Raqa, the jihadists' de facto Syrian capital.

The death came as Americans celebrated the Thanksgiving holiday.