Syrian aircraft pounded rebel-held areas of Aleppo for a third day on Tuesday, with hospitals reportedly overwhelmed as more than 100 people have been killed in the bombing, AFP reports.
Two children were among at least 20 people killed in Aleppo on Tuesday, according to the Syrian Observatory for Human Rights, a Britain-based group that relies on activists and other witnesses in Syria.
Air strikes on rebel-held areas Sunday and Monday killed 86 people, including 32 children, the Observatory told AFP.
On Sunday, the Observatory said that the Syrian army had dropped explosive-laden barrels on rebel-held areas of Aleppo, causing the large numbers of victims.
Aleppo, Syria's second city and onetime commercial hub, emerged as a key front after a rebel offensive last year. The northern city is today split between regime and rebel-controlled enclaves.
The city has also been one of the regions in Syria where a second civil war has erupted, between Islamist rebels and the more moderate, Western-backed rebels seeking to topple President Bashar Al-Assad.
Months ago, the 13-member Islamic Front for the Liberation of Syria split off from the main Syrian National Council opposition force and declared Aleppo to be an independent Islamist state.
The Islamists subsequently turned on the moderate rebel groups. Last month a number of Syria's largest Islamist rebel groups united under the banner of the Islamic Front, putting their joint force of up to 60,000 fighters under one single command.
An estimated 126,000 people have been killed in Syria's civil war, which erupted after a brutal crackdown on pro-democracy protests first held in March 2011.
Meanwhile, international humanitarian organization Doctors Without Borders corroborated reports that regime helicopters started dropping barrel bombs on Aleppo on Sunday.
In just two cases -- the targeting of a school and a roundabout where people wait for public transport -- "there were dozens of dead and injured people," the organization’s Syria coordinator, Aitor Zabalgogeazkoa, told AFP.
"A dozen bodies were being lined up in front of three hospitals waiting to be recovered by the families."
“The hospitals in the area are overrun and are asking for medical supplies. We sent them immediately,” Zabalgogeazkoa said.
Earlier, the Observatory and activists said the air force had been dropping barrels of explosives from both helicopters and fixed-wing aircraft.
Observatory director Rami Abdel Rahman said there was a "marked escalation" in attacks, and that "this type of intensive bombing over several days demonstrates the desire of the army to advance" on rebel-held areas.
The opposition National Coalition said the "systematic raids on Aleppo demonstrate the regime's rejection of a political solution" to the war.
It also accused the international community of "indifference" and of being "seemingly incapable of taking a firm position to guarantee a stop to the bloodshed."