HRW said two opposition Free Syrian Army facilities in the vicinity might have been targets of the Syrian aircraft.
One was the headquarters of the local Free Syrian Army brigade two streets away from the block that was hit. The other was a detention facility where the Free Syrian Army held "security detainees" government military personnel and members of pro-government shabiha militia. Neither of these facilities was damaged in the attack.
Azaz, which is home to around 35,000 people, is also the town where rebels have been holding 11 Lebanese Shiites they captured in May. On Wednesday, Lebanese media reported conflicting reports on their fate, but it was unclear whether they had been affected by the bombing.
In Damascus, the U.N. humanitarian chief Valerie Amos said the Syrian conflict has "become more intense and is too often indiscriminate."
"All parties must do more to protect civilians," said Amos at the end of the three-day mission to try to open more channels for international aid inside Syria.
She observed that "the humanitarian situation has worsened" since her last visit to Syria in March, when the U.N. estimated more than 1 million people had been displaced or in need of critical humanitarian aid. "Now as many as 2.5 million are in need of assistance," she said.
Later in Beirut, Amos expressed frustration at Syria's reluctance to allow more major international aid groups into the country because of Syrian fears that relief supplies could reach rebels.
"They don't want to see that happen," she said.
France's foreign minister said that while humanitarian aid was needed, "we also need political action to achieve replacing Bashar Assad, and we need action on the ground carried out by the rebel army."
Assad is "butchering his own people and the sooner he goes the better," Laurent Fabius said during a visit to Jordan, where France has set up a military field hospital to treat Syrian refugees.
Syrian state-run TV said Assad named three new Cabinet ministers. One replaced former Health Minister Wael Nader al-Halqi, who became the new prime minister after his predecessor Riad Hijab defected to Jordan.
The other two who were replaced are the justice and industry ministers. There was no immediate indications why Assad ordered the reshuffle or whether they were related to any possible new defections. Just before Hijab's defection was announced earlier this month, he was sacked from his job by Assad.
Assad also appointed a new governor for Aleppo province.
Also on Thursday, state-run television said government troops freed three journalists who were seized last week by rebels while covering violence in a Damascus suburb.
Syria TV says the three journalists from the pro-regime TV station Al-Ikhbariya were freed in a "qualitative operation" Thursday in the town of al-Tal just north of the capital. It did not provide further details.
The Syrian Observatory for Human Rights also said the Al-Ikhbariya team was freed, amid heavy shelling on al-Tal. The group relies on a network of activists on the ground.
In another symbolic blow to Syria, the Organization of Islamic Cooperation suspended Syria from the group during a meeting in Saudi Arabia. The move brought a swift denunciation from Iran, Assad's main regional ally.
Iran's foreign minister, Ali Akbar Salehi, criticized the decision as "unfair" because Syria was not invited to the Mecca summit, which wrapped up early Thursday. Saudi Arabia is among the chief backers of the Syrian rebels.