Dozens of civilians including 12 from the same family were killed Monday in heavy bombardment of east Aleppo despite Western warnings of sanctions against Syria's regime over attacks on the city.
Once Syria's thriving commercial hub, Aleppo has been ravaged by bombing raids and intensifying clashes as President Bashar al-Assad's forces fight to capture rebel-held parts of the city.
Russian air support for the onslaught -- which has destroyed hospitals and other civilian infrastructure -- has spurred accusations of potential war crimes and threats of punitive sanctions.
World powers are expected to follow up Monday on last-ditch efforts at the weekend aimed at ending Syria's five-year conflict.
The latest air strikes on Aleppo killed 13 civilians in the rebel-held district of Marjeh, including 12 members of the same family, said the Syrian Observatory for Human Rights.
"Nine of the family members were minors, including a 17-year-old girl and her newborn," said the Britain-based monitoring group's head Rami Abdel Rahman.
The deaths brought to 47 the number of people killed since Sunday morning in east Aleppo, the Observatory said.
Bombardment has been so heavy in recent days that streets have been blocked off by massive piles of rubble from destroyed buildings, an AFP correspondent said.
- 'It's a disaster' -
The deadliest raids were overnight on a residential block in Qaterji, where the Observatory said Russian strikes killed 18 civilians.
"There are still families under the ruins. We pulled out seven or eight bodies and dozens of wounded," said ambulance driver Abu Mohamed.
"The hospitals are full of casualties. It's a disaster."
One of those rescued was Maarouf, a 12-year-old whose leg had been trapped under rubble on the upper floor of a residential building.
A White Helmet volunteer in a crane could be seen approaching the boy, who was clad in a dust-covered shirt and wriggling in vain to get himself free.
Maarouf was extracted and his injured right leg treated at a field hospital.
But White Helmets rescuers later emerged with a dead baby cradled in a blanket, her face caked in dust.
Both Russian and Syrian warplanes are carrying out air strikes over Aleppo city in support of a major offensive by regime forces to capture rebel-held neighbourhoods.
More than 430 people have been killed in bombardment on the eastern half since the assault was announced on September 22, the Observatory said.
Another 82 have died in rebel fire on government-held neighbourhoods in the west.
Further west in Aleppo province, Russian raids killed 23 people in the village of Uwaijal on Monday, said the Observatory.
- 'Extra measures' on Moscow? -
In response to the onslaught, the US and Britain warned at the weekend that they were considering new economic sanctions against Syria and Russia.
"There are a lot of measures that we're proposing including extra measures on the regime and their supporters," said British Foreign Secretary Boris Johnson.
French Foreign Minister Jean-Marc Ayrault said the ministers would "examine all the options to put much stronger pressure on the regime of Bashar al-Assad and his allies".
But the European Union's foreign affairs head Federica Mogherini said the bloc of countries was not yet considering sanctions against Russia.
"This has not been proposed by any member state," Mogherini said as she arrived for a meeting of EU foreign ministers dominated by the Syrian crisis.
"But we have sanctions on the Syrian regime... and there are discussions on that, for sure, that could be possible."
US Secretary of State John Kerry met with his counterparts from Russia, Iran, and Syria's neighbours in Switzerland on Saturday, then travelled to London for meetings with Johnson and other European officials.
Kerry said the Lausanne meeting produced new ideas on reviving a Syrian truce but said high-level contacts to flesh them out would continue Monday.
Syria's war has devolved from a widespread protest movement against Assad's rule to a multi-front war between rebels, jihadists, Kurds and regime forces.
Turkish-backed rebel fighters dealt a major symbolic blow to the Islamic State jihadist group on Sunday by overrunning the northern Syrian town of Dabiq.
Across the border in Iraq, Prime Minister Haider al-Abadi announced the launch Monday of a long-awaited operation to recapture Mosul -- IS's last major stronghold in the country.
In June 2014, IS declared a self-styled Islamic "caliphate" in territory straddling Syria and Iraq.
