The London-based Syrian Observatory for Human Rights said it was not immediately clear how many of the dead were from the crash at a residential area in Ariha, in Idlib province, and how many from the prior bombardment.
"It was flying at a low altitude when it had a mechanical failure," Rami Abdel Rahman, the Syrian Observatory's head, said, citing medical officials and residents inside the town.
"At least 23 people, including two children, were killed. Five of them have not been identified."
He said at least 70 people were wounded.
"Six people are still under the rubble, and we don't know if they are alive or dead," he said.
The pilot's fate
The Syrian Observatory, which relies on a wide network of activists, medics, and fighters throughout Syria, said the fate of the pilot was unknown.
Another activist group known as the Local Coordination Committees said it was not immediately clear whether the plane was shot down.
It said 27 people were killed and many others were wounded.
It has lost a number of aircraft, some to enemy fire, some to mechanical failure.
In mid-January, at least 35 government troops were killed when a military aircraft crashed in Idlib.
The province has since been largely overrun by an anti-government alliance including al-Qaeda's Syria affiliate, the Nusra Front, which seized Ariha on May 28.
The Nusra Front said on Friday it had captured "moderate" fighters who had received training from the US.
The group also accused the US of recruiting forces from what it calls "the moderate opposition" to undergo a training and rehabilitation programme run by the CIA.
UN announcement
The latest developments come amid a US announcement that it plans to provide, together with Turkey, air cover for Syrian fighters.
US officials, first quoted by the Wall Street Journal newspaper, said the US would provide offensive strikes to support advances against Islamic State in Iraq and the Levant (ISIL) targets.
The US would also provide defensive support to repel any attackers.
US officials have long played down the idea that Assad's forces - which have not fired on US-led coalition aircraft bombing ISIL targets in Syria - would turn their sights on the US-backed Syrian fighters.
But they cannot rule out the possibility, perhaps in an unintentional clash.
