Medical personnel look for survivors following a reported airstrike on the Tariq al-Bab district of the northern Syrian city of Aleppo on February 1, 2014.
(CNN) -- Ninety people were killed in a day of punishing air assaults on Aleppo as so-called barrel bombs rained down on the city, an opposition group said.
Women and children were among the victims in Saturday's raids in various neighborhoods in the rebel stronghold, the UK-based Syrian Observatory for Human Rights said Sunday.
It added that 10 fighters from the radical Nusra Front were killed when their headquarters were targeted. Nine people were killed near Aleppo's central prison, it said.
Barrel bombs -- drums packed with explosives and shrapnel -- can level entire buildings with one hit.
In four hours, the area of Ansari was targeted with about 17 air strikes, one medical staffer from a field hospital in Aleppo told CNN.
"The humanitarian situation is very bad, there is a huge number of wounded people," he said from the Turkish border, where he had gone to get supplies.
"I am so nervous because my staff inside (have) become so confused, I have to calm them, I don't know what I will have to do for tomorrow."
In a report released Thursday, Human Rights Watch said the Syrian government "deliberately and unlawfully" demolished thousands of homes in rebel strongholds in the cities of Damascus and Hama in one year.
CNN cannot independently verify daily death tolls, but the United Nations says more than 100,000 people have been killed in Syria since 2011.
Aleppo has come under punishing, sometimes near-daily, air raids.
"The situation is very urgent," the medic said. "We need U.S. pressure on the regime for us to be able to take a breath, to have them stop this aggressive shelling on Aleppo."
He said all the roads to the city were blocked.
The Syrian government has previously said the operations are targeting "terrorist groups" in neighborhoods of Aleppo.
News of the bombings came after a first round of Syrian peace talks ended in Geneva on Friday with no progress towards ending a nearly three-year civil war.
The contentious first round began with bitter exchanges and repeatedly seemed on the verge of collapse before the two sides entered the same room.
The next round of negotiations is due to start February 10 but the government has been unable to say whether it will return.
According to Syrian state news agency SANA, Foreign Minister Walid al-Moallem ruled out any direct talks with the U.S. unless "Secretary of State, John Kerry, apologizes for what he had said during the opening speech of the conference."
In opening remarks, Kerry said the path to peace had to involve the world community and could not include Syrian President Bashar al-Assad, whom he accused of widespread human rights abuses.
The conflict has also been mired by accusations that the Damascus government used chemical weapons and that the opposition includes al Qaeda-affiliated groups.
"This is a modest beginning, but it is a beginning on which we can build," U.N. special envoy Lakhdar Brahimi told reporters after the talks ended Friday.
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