The first responders and local activists reported a lower death toll, saying at least 20 people had been killed.
The jets hit as the mosque was full of worshippers during evening prayer, according to the British-based observatory.
Soon after an airstrike by the USA military in northern Syria against an al Qaeda target Thursday evening, the military denied targeting a mosque deliberately, where at least 42 people were killed, reports said. The group's second-in-command, Abu al-Khayr al-Masri, was killed in an air strike on his vehicle late February, and the USA said that a separate bombing raid on an al-Qaeda training camp in January killed more than 100 militants. Syrian and Russian warplanes commonly operate in the area around Jineh, targeting rebels, and U.S. warplanes have also carried out airstrikes nearby against al-Qaeda targets recently.
The volunteer Syrian Civil Defence rescue service said dozens of people remain buried under rubble.
The US military said it carried out an air strike on Thursday against al Qaeda militants, killing several, at a meeting location in Idlib province, but it was unclear if it was referring to the attack on Al-Jinnah.
"You can see the destruction, so it's not clear exactly how it's possible that one part was hit, the other parts wasn't them", Kareem said in the video. "It was right after the prayer at a time when there is usually religious lessons for men in it". "We couldn't even recognise some of the bodies", he added.
Footage published by Halab Today, an online media group focused on news in Aleppo, showed piles of rubble where the mosque allegedly stood.
The group said most of those killed were civilians.
The observatory said it was unable to determine whose planes carried out the raid.
Syrian and Russian military have also carried out many air strikes in Idlib and Aleppo provinces during the war.
Russian Federation began a military intervention in Syria in September 2015, and in the past has dismissed allegations of civilian deaths in its strikes.
The US-led coalition fighting the Daesh group said earlier this month that its raids in Iraq and Syria had unintentionally killed at least 220 civilians since 2014. Critics say the real number is much higher.