The Local Coordination Committees said the warplane crashed in a busy market in Ariha, adding that it was not immediately clear whether the warplane was shot down.
Rami Abdurrahman, who heads the Britain-based Syrian Observatory for Human Rights, said the warplane crashed in the center of the town, destroying several homes and killing at least 12 people.
The town of Ariha, once a government stronghold, was captured by opposition fighters and Islamic militants in May. The town is in the northwestern province of Idlib, where government forces have suffered setbacks since March, including the loss of the provincial capital, which is also called Idlib.
The Observatory and the Local Coordination Committees said that at the time of the crash, the town was under attack by the air force of embattled Syrian President Bashar Assad.
An amateur video posted online by activists showed several damaged buildings, as well as parts of the plane that crashed. The video appeared genuine and corresponded to other Associated Press reporting of the events.
Syria’s civil war began in March 2011. The United Nations says the war has killed more than 220,000 people and wounded at least 1 million.