In fresh strikes, Russian and Syrian regime jets pounded opposition-held parts of Aleppo early on Thursday, said the Syrian Observatory for Human Rights (SOHR). Severe bombardment on Syria's biggest city has killed at least 84 civilians including children, the monitor and a civil defence official said.
The fresh aerial assault was accompanied by the regime's advance on the northeastern outskirts of Aleppo, where its forces captured several hilltops overlooking the opposition-held areas.
Air strikes killed 13 people on Thursday, when warplanes hit several rebel-held districts, including al-Kalaseh, Bustan al-Qasr and al-Sakhour, civil defense official Ibrahim Abu al-Laith told Reuters from Aleppo.
Seven children were among 71 civilians killed in opposition-held areas on Tuesday and Wednesday, SOHR head Rami Abdel Rahman said.
"The toll jumped because there were so many people who died of their wounds, and others whose bodies were still stuck under the rubble," he added.
The Syrian regime forces launched the offensive to retake the whole of Aleppo on September 22. Eastern Aleppo has been held by the opposition fighters since 2012. Up to 300,000 people are still believed to be trapped in the besieged parts of the city.
The regime operation has been backed by Moscow, which stepped up its air strikes against opposition-held areas earlier this week.
A ceasefire in Syria brokered by the US and Russia collapsed last month. The Russian government and Syrian regime blamed their foes for breaking the ceasefire.
Russia, last week, vetoed a UN Security Council resolution chalked out by France calling for an end to the bombings in Aleppo.
Kerry and Lavrov to meet in Switzerland
US officials on Wednesday said US Secretary of State John Kerry will meet his Russian counterpart in Switzerland on Saturday to discuss Syria. The meeting will include foreign ministers from Turkey, Qatar, Saudi Arabia and Iran.
Earlier, Kerry broke off talks with Russian Foreign Minister Sergei Lavrov over the offensive, which included air strikes on hospitals. The US and France termed the assaults "war crimes," and said Syria and Russia were responsible.
The resumption of talks, despite the offensive, underlined the lack of options facing Western nations over the Syria conflict.