A six-year-old boy has been miraculously rescued from the rubble in eastern Aleppo after a third day of renewed air strikes in the rebel-held city.

In a four-hour effort to save the boy, Syrian Civil Defence volunteers, also known as the White Helmets, saved Mohammad in the neighbourhood of al-Ma’adi, where the attacks occurred.

Reports are saying three civilians have been killed in the air strike, while several others were injured.

Overall, the third day of air strikes and shelling have killed at least 25 people, according to a group that monitors Syria’s civil war.

The mayor of the besieged sector, meanwhile, has warned of an acute lack of fuel and food as winter encroaches.

The bombardment of eastern Aleppo restarted on Tuesday after a four-week pause, part of a wider military escalation against insurgents by the Syrian government and its allies, including Russia.

The battle for Syria’s second city marks a crucial phase of the five-year civil war, in which hundreds of thousands of people have been killed, and its capture would be a major triumph for President Bashar al-Assad.

His government said on Tuesday it was striking what it called “terrorist strongholds” in Aleppo.

Health officials in the opposition-held part of Aleppo said they had recorded 45 deaths and admitted 363 wounded people as a result of air strikes up to and including Wednesday this week.

Russia says it is not bombing the city, but it is using an aircraft carrier, missiles fired from another warship, as well as planes launched from air bases in Russia and Syria to strike targets around the country.

The siege and intense bombardment of east Aleppo have created a dire humanitarian crisis, aggravated by frequent air strikes on hospitals and the disruption and pollution of water supplies. Medicines, food and fuel are severely depleted.

“There is only enough to keep the bakeries going to give people at least some bread. People are only getting about 15 per cent of what they need,” Brita Hagi Hassan, president of the city council for opposition-held Aleppo, told Reuters.

Wounded kids wait to receive medical treatment at the Sahra hospital following an Aleppo air strike. Photo: Getty

The United Nations says 250,000 civilians remain in Aleppo’s opposition-controlled neighbourhoods, effectively under siege since the army, aided by Iranian-backed militias and Russian jets, cut off the last road into rebel districts in early July.

International charity Oxfam said it had moved a large electricity generator to the Suleiman al-Halabi water station that is located on the frontline between east and west Aleppo and still serves both sides of the city under an agreement.

It said all other aid to the besieged area remains cut off.

Aerial footage of Aleppo on November 4

The Syrian Observatory for Human Rights, a Britain-based organisation that monitors the war, said shelling and air strikes from helicopters and jets hit the eastern half of the city, causing severe damage.

Air strikes also hit rebel-held areas west and south of Aleppo.

Shelling of government-held western Aleppo by rebels during a failed counter-attack they staged earlier this month killed dozens of people, the UN said.

A senior official in the military alliance fighting in support of Assad told Reuters last week the plan was to recapture the city before US President-elect Donald Trump takes office in January.