Air strikes and intense artillery fire have pounded the rebel-held east of the Syrian city of Aleppo for a fourth day running, monitors and rescuers say.
An AFP correspondent in the Syrian city said the shelling was the most intense he had heard in two years.
Thirteen people were reported killed in the province - three hit by rebel rockets in government-held areas.
The UN's Syria humanitarian adviser said east Aleppo faced a "bleak moment" with supplies low and winter coming.
"My understanding is that virtually all warehouses are now empty and tens of thousands of families are running out of food," Jan Egeland told Reuters.
Najib Fakhoury, a volunteer with the White Helmets Civil Defence force, told the French news agency AFP he had "never heard such intense artillery bombardments".
His team had been unable to respond to an emergency call because "the shells are falling on the street", he said.
The Syrian Observatory for Human Rights, a UK-based monitoring group, said at least 18 different neighbourhoods in east Aleppo had been hit.
At least three people had died in east Aleppo, as well as seven in Arada, a town in the south-west of Aleppo province, and another six in Reef Dimashq province, the group said.
The Syrian official news agency Sana said "terrorist" rockets had killed three people in Aleppo and one in a Damascus neighbourhood.
There were reports that the only paediatric hospital remaining in the besieged part of Aleppo had been hit again, two days after medics and activists said that it was badly damaged.
On Thursday the head of the hospital, Dr Hatem, told the BBC his hospital had just two weeks' worth of medical supplies left.
Aleppo, once Syria's commercial and industrial hub, has been divided roughly in two since 2012, with the government controlling the west and rebels the east.
On 22 September, two weeks after encircling the east and reimposing a siege on its estimated 275,000 residents, the army launched an all-out assault to take full control of the city with the help of Iranian-backed militias and the Russian air force.
By the end of October, air strikes and shelling had killed more than 700 civilians in the east, while rocket fire had left scores dead in the west, according to the UN.
The air strikes resumed on Tuesday after a three-week moratorium declared by the government's ally Russia ended, with at least 65 killed in the past four days.
However, on Thursday, Russia said its air force was only active in Idlib and Homs provinces, targeting so-called Islamic State and not operating over Aleppo.