Air attacks by the Syrian government have killed at least 30 people, including children, in the rebel-controlled town of Azaz, about 45km north of Aleppo, according to opposition activists.
Witnesses and Free Syrian Army (FSA) forces who reinforced security around the town after the raids said the jet fired twice, targeting a makeshift media centre used by foreign reporters in the second, smaller attack.
Most of the injured from Wednesday's attack were driven directly to the Turkish border, 6km north.
Dozens of people, many wailing and shouting, were climbing over the rubble, trying to pull out victims.
"That's it, I'm leaving for Turkey with my family today. Life here is impossible," a witness, who gave his name as Jomaa, said.
"If you come to the basement of my house now, there are 15 women who are afraid to go out. This is what Bashar does to us."
The bombings did not appear to hit specific rebel targets, though one of the sites was about 1km away from the local rebels' political and media offices.
"Bashar did this. God help us, these animals will kill us all," said one man, hoisting a bloodied arm that had been piled up on the pavement outside the hospital in Azaz after the bombardment.
Al Jazeera's Stefanie Dekker, reporting from Antakya, a Turkish town near the Syria border, said: "We know that it started around 3 o'clock in the afternoon when the jets came and started bombing an area of the town, their target we were told was a former Baath headquarters which is now where the Free Syria Army have their base.
"But as you could see from those pictures it is mostly civilians who where affected by the air strikes. A whole row of residential homes have been completely levelled, with horrific pictures of children trapped underneath the rubble."
Witnesses said shortly after the attack that at least five bodies had been pulled from the rubble and many more were still trapped.
"This was a civilian area. All these houses were packed with women and children sleeping during the fast," said witness Abu Omar, a civil engineer in his 50s, referring to the dawn-to-dusk fast Muslims observe during Ramadan.
The attack came amid heavy shelling of several districts of Aleppo, regarded as a pivotal battleground in the conflict that is now entering its 18th month and has killed more than 23,000 people, according to activists.
Al Jazeera's Dekker said it seems like it is a clear message from the government to the opposition that says they do not want the rebels there.
"Azaz is a critical town for the opposition since it's close to the Turkish border where it offers them a free way in and out of Turkey into Azaz and on to Aleppo," she said.
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Footage from an amateur video distributed by the UK-based watchdog group, Syrian Observatory for Human Rights, also showed the immobile, dust-covered hand of a little girl, likely dead, reaching out from under ruined buildings.
Witnesses said the bomb must have weighed at least half a tonne and the impact shattered windows up to four blocks away.
Residents insisted there was no rebel base where the bomb struck, but some said the families of FSA fighters lived there.
On the pavement outside the hospital, body parts had been heaped in a pile under a blanket.
"Nobody knows how high the toll will climb now. It could take days to finish searching through the rubble," said Abu al-Baraa, a doctor who had just arrived in Syria from Saudi Arabia to help.
"I'm a radiologist, not a surgeon, but I'll do anything I can to help. There is only one other doctor at Azaz hospital, an anaesthetist."
Meanwhile,reports say at least 25 people have been killed in government shelling of Qadi Askar district in Aleppo.
Also on Thursday, Valerie Amos, the United Nations humanitarian chief, have said on Thursday as many as 2.5 million people were in need of aid in Syria, where al-Assad's forces have been fighting rebels seeking his overthrow for 17 months.
Speaking in Syria where she met Wael al-Halki, the Prime Minister, and other officials this week, Amos urged government forces and rebels to do more to protect civilians caught up in the violence.