According to the UK-based Syrian Observatory for Human Rights, which relies heavily on a network of spies working for the foreign-backed opposition, the USA warplanes had attacked the mosque, killing 42 people, and injuring more than 100 others.
The Britain-based Syrian Observatory for Human Rights said at least 46 people were killed, mainly civilians.
ISIS had at one point held the area around al-Jineh as part of its push into the northwestern part of Aleppo, but appears to have been expelled.
A USA military official told Agence France-Presse that American forces carried out raids against an Al Qaeda faction in Aleppo's Al-Jinnah neighborhood, reportedly killing several suspected terrorists. "Bodies filled the space", said Mohamed al-Shaghal, a local journalist who arrived at the scene shortly after the attack.
A USA -led coalition Rockwell B-1 Lancer flies above the Syrian city of Kobane on November 5, 2014.
Much of the building, identified by a black placard outside as a mosque, had been flattened.Residents said that they had been warned that jets from the US-led... The group's second-in-command, Abu al-Khayr al-Masri, was killed in a strike last month, and Centcom said that a separate bombing raid on an al Qaeda camp in January killed more than 100 militants.
But the skies over Aleppo province are busy, with Syrian regime and Russian warplanes as well as US-led coalition aircraft carrying out strikes.
But U.S. Central Command says it has intelligence showing that the mosque was across a street from the building where the al Qaeda leaders were meeting.
The area is home to hundreds of thousands of Syrians displaced by fighting.
The rival Hayat Tahrir al-Sham, a powerful jihadist alliance in northwest Syria, also blamed the US -led coalition.
More than 320,000 people have been killed in Syria since the conflict began six years ago with anti-government protests.