The Britain-based Syrian Observatory for Human Rights said 23 people died in the double airstrike and more than 200 were wounded. Mohammed Nour, a local activist reached by phone, put the death toll at 25. Neither figure could be independently confirmed.
Reporters from The Associated Press saw nine dead bodies in the bombings' immediate aftermath, including a baby.
The bombings sent panicked civilians fleeing for cover.
A group of young men found a man buried in the wreckage of destroyed homes, his clothes torn and his limbs dirty, but still alive.
"God is great! God is great!" they chanted as they yanked him out and laid him on a blanket.
Nearby, a woman sat on a pile of bricks that once was her home, cradling a dead baby wrapped in a dirty cloth. Two other bodies lay next to her, covered in blankets. She screamed and threw stones at a TV crew that tried to film her.
The bombing of Azaz, some 30 miles (50 kilometers) north of Aleppo, shattered the sense of control rebels have sought to project since they took the area from President Bashar Assad's army last month. Azaz is also the town where rebels have been holding 11 Lebanese Shiites they captured in May.
The attack came on the same day the U.N. released a report accusing Assad's forces and pro-government militiamen of war crimes during a May bloodbath in the village of Houla that killed more than 100 civilians, nearly half of them children.
The long-awaited report by the U.N. Human Rights Council marks the first time the world body has referred to events in Syria as war crimes—on both the government and rebel sides—and could be used in future prosecutions against Assad or others.
It said the scale of the Houla carnage indicated "involvement at the highest levels" of Syria's military and government. The council also said the conflict is moving in increasingly brutal directions on both sides.
Also on Wednesday, the Organization of Islamic Cooperation, comprised of 57 member states, released a final statement from its two day summit in Saudi Arabia's Muslim holy
Iran's Foreign Minister Ali Akbar Salehi, whose nation is Assad's most staunch regional supporter, told reporters before the opening session in Saudi Arabia that suspending Syria will not resolve the issue of the unrest there.
A wide-ranging tableau of violence and retributions on Wednesday reinforced the U.N.'s warnings.
A blast in central Damascus rattled—but did not injure—U.N. observers, followed by the airstrikes in Azaz. And in tense Lebanon, a powerful Shiite clan that backs Assad said it abducted at least 20 Syrians in retaliation for rebels holding one of their relatives captive in Syria. The rebels accuse the Lebanese man of belonging to Hezbollah, a Shiite Lebanese group allied with Syria and Iran.
The bombing of Azaz brought into stark relief the limits of the rebels' expanding control of Syria's north.
In recent months, rebels have pushed the Syrian army from a number of towns in a swath of territory south of the Turkish border and north of Aleppo, Syria's largest city. About a dozen destroyed tanks and army vehicles are scattered around Azaz, left over from those battles.
As the Assad regime's grip on the ground slips, however,
Rebels and residents of the Aleppo countryside say the army rarely hits rebel targets, striking instead at residential areas and killing civilians.
The Azaz bombings appeared to fit that pattern.
The first blast seemed to come out of nowhere, shaking the city's downtown and sending up a huge gray cloud of smoke that sent terrified residents rushing through the streets looking for cover.
Not long after, another jet appeared, dropping bombs nearby.
"We were in the house and heard this plane overhead," said a 36-year-old woman who gave her name as Um Hisham. "There was this huge boom that made my mother pass out in the kitchen."
Hundreds of residents flocked to the bombing sites to inspect the damage and look for dead and wounded in the rubble.
The first blast damaged houses and shattered shop windows along nearby streets. It sheared off the front wall of one home, exposing a man and his wife inside their kitchen, where jars of olives and pickles still sat in the cupboards.
"I saw the plane come down and some missiles fall and then there was smoke all over," said Mohammed Fuad, 18. "When it cleared, we heard screaming and saw rubble all over the streets."
More than a dozen homes were reduced to a huge expanse of broken concrete. Men wandered the area, lifting up bricks and peering through holes in collapsed roofs to see if anyone was stuck underneath.
One group brought a generator and an electric saw to cut through rebar, while others cleared rubble from the road so pickup trucks ferrying the dead and injured could pass.
Many of those gathered screamed at foreign journalists, decrying the international community for not intervening militarily in Syria's civil war. The revolt that started in March 2011 with protests calling for political change has killed more than 20,000 people, activists say.
Many of the wounded were driven directly to the Turkish border, four miles (six kilometers) to the north.
Nour, the local activist, said there were 15 dead in a hospital in Turkey and 10 who had been buried in the town. He said many more had yet to be counted.
The area appeared to be no more than a poor, residential neighborhood with a few metal workshops, and residents said there were no rebel bases there, though they often do not speak openly about where rebels operate.
Azaz has considered itself "liberated" since rebel forces pushed out the army last month. Its largest rebel group, the Northern Storm Brigade, runs a prison and the nearby border crossing with Turkey. It's political and media offices are less than a mile (kilometer) away from the bombing site, in the former local headquarters of Assad's Baath party.
Along with about 15 Syrian prisoners, the rebels are currently holding 11 Lebanese Shiites they detained a month ago. Nour, the activist, said four of them were missing after the bombing, though he was not sure if they had been killed. He said the building they were being held in was hit.
About a dozen rebel fighters in camouflage vests flocked to the scene after the bombings, scanning the skies for more jets. None of them carried more than a Kalashnikov rifle.
In nearby Aleppo, activists reported shelling and clashes in the city, where rebels have taken control of several neighborhoods over the past weeks. The Syrian Observatory for Human Rights said the rebels were trying to take over a key dam in the northern town of Manbij, east of Aleppo. It said the army was using helicopter gunships in the battles along the Euphrates River.
U.S.-based Human Rights Watch said Syrian government fighter planes fired rockets that struck the main hospital in an opposition-controlled area of Aleppo a day earlier, wounding two civilians and causing significant damage. The group said its members visited the damaged hospital.
There were fresh signs Wednesday that the civil war was spilling across the border into Lebanon, a country ravaged by its own 15-year civil war that Syria was deeply involved in, and which is sharply divided between supporters and opponents of Assad's regime.
Syrian rebels have adopted a new tactic of seizing prisoners from countries or foreign groups allied with the regime to rattle Assad and his allies outside the country, such as the 11 Lebanese Shiites captured in May shortly after they crossed from Turkey on their way to Lebanon. Earlier this month, rebels abducted 48 Iranians near the capital, Damascus.
On Wednesday, Sunni power Saudi Arabia ordered its citizens to leave Lebanon, citing fear of kidnappings by Shiites angry over the rebels taking prisoners from Lebanon and Iran.
In Damascus, a bomb attached to a fuel truck exploded Wednesday outside a hotel where U.N. observers are staying, wounding at least three people, Syrian state TV reported. Activists also reported clashes near the government headquarters and the Iranian Embassy in Damascus.
AP writers Suzan Fraser in Ankara, Albert Aji in Damascus, John Heilprin in Geneva and Abdullah al-Shihri in Riyadh contributed to this report.