BEIRUT (AP) -- Hospitals in the northern Syrian city of Aleppo are overwhelmed with casualties, an international aid group warned Tuesday, as government warplanes blasted opposition areas of the city as part of a withering three-day air assault that has killed more than 100 people.
The intensified air campaign, which one activist group in the city called "unprecedented," suggests President Bashar Assad's government is trying to crush opposition in the contested city, Syria's largest, ahead of an international peace conference scheduled for late January in Switzerland.
Aleppo has been a major front in Syria's civil war since the rebels launched an offensive there in mid-2012, and the city has since been carved into opposition- and government-held areas. On Tuesday, the main Western-backed opposition group, the Syrian National Council, accused the international community of "failing to take any serious position that would guarantee a stop to the bloodbath" ahead of the peace talks.
The Britain-based Syrian Observatory for Human Rights said airstrikes Tuesday killed 15 people, including two children, in the rebel-held Shaar district.
An amateur video posted online showed the aftermath of one of the strikes: rescue workers in white hard hats pulling a man from the rubble of a shattered apartment building. A crowd of people in the street shouted "God is greatest!" as the rescuers rushed the dust-covered man to a waiting ambulance. The video appeared genuine and corresponded to other AP reporting.
Tuesday marked the third consecutive day that Aleppo has been hit by deadly government airstrikes.
On Sunday, at least 76 people, including 28 children, died in air raids, according to the Observatory. Other opposition groups reported higher death tolls. Another round of government airstrikes Monday killed at least 12, the Observatory said.
The aid group Doctors Without Borders said in a statement Tuesday that hospitals in Aleppo have been overwhelmed by the massive influx of wounded from the attacks, which have "emptied stocks of critical drugs and medical materials for lifesaving procedures."
"Repeated attacks often lead to chaos and make it more difficult to treat the wounded, thereby increasing the number of fatalities," said the group's coordinator in Syria, Aitor Zabalgogeazkoa. "The ambulances are overwhelmed because they are called to several areas at the same time. Doctors face extremely difficult decisions because they receive such a significant flow of patients."
Doctors Without Borders, which provides Aleppo hospitals with medical supplies, said the latest attacks were "exacting a cumulative effect on already exhausted health care facilities."
Syria's nearly 3-year-old conflict appears to have escalated in recent weeks as both sides maneuver ahead of next month's planned peace talks, and despite calls for a cease-fire.
The latest came from U.N. Secretary General Ban Ki-moon, who on Monday demanded a halt to the hostilities. Speaking to reporters in New York, he said the situation in Syria has "deteriorated beyond all imagination" and insisted that the fighting stop before political dialogue on Syria can start.
The U.S.- and Russian-brokered peace conference between Assad's government and the Syrian opposition is scheduled to begin in January in the Swiss city of Montreux. Plans are underway to organize a one-day meeting of foreign ministers in the city ahead of the Syrian talks, U.N. officials said Tuesday.
U.S. Secretary of State John Kerry, Russian Foreign Minister Sergey Lavrov and more than two dozen other foreign ministers are expected to gather for the Jan. 22 meeting at a Montreux hotel.
The conference will reconvene on Jan. 24 for the start of actual negotiations between Syria's warring sides, said Khawla Mattar, a spokeswoman for the U.N.'s special envoy to Syria, Lakhdar Brahimi.
Civilians continue to pay the highest price in the conflict after even the most modest attempts at peace have failed.
On Monday alone, at least 150 people were killed nationwide, according to the Observatory, which relies on a wide network of activists on the ground. Most of the casualties were reported in and around Syria's largest cities, including in the capital, Damascus, Aleppo and the central city of Homs.
The high daily death toll coincided with the United Nations' $6.5 billion appeal to help displaced Syrians and their host countries as civil war is expected to rage on well into 2014.
Nearly 9 million Syrians have been uprooted from their homes, with some 2.3 million fleeing into neighboring countries and millions of others searching for shelter in safer parts of Syria.
Associated Press writers Barbara Surk and Zeina Karam in Beirut, and John Heilprin in Geneva contributed to this report.
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