More than two dozen people are feared dead or injured after a fighter plane crashed during an air raid.

The warplane came down in the center of Ariha, Syria, destroying several homes and killing at least 27 people, according to the British-based Syrian Observatory for Human Rights.

The military plane bombed the heart of the city center and the main commercial street before crashing in the middle of the marketplace, two witnesses told Reuters.

"The plane had dropped a bomb on the main Bazaar street at low altitude only seconds before it crashed," Ghazal Abdullah, a resident who was close to the incident, told Reuters.

The Observatory for Human Rights, which tracks violence across Syria, said most of the dead were civilians who were on the ground in the Idlib provincial town.

Ariha, once a government stronghold, fell to opposition fighters and Islamic militants in May. The town is situated in the northwestern province of Idlib. It is an area where government forces have suffered setbacks since March, including the loss of the provincial capital, which is also called Idlib.

Fighting between government forces and an insurgent group called Jaish al Fateh, or Army of Conquest, which includes al Qaeda-linked Nusra Front, has intensified in rural Idlib province in recent times, according to Sky News.

The surge in hostilities comes after U.S. officials admitted the Pentagon will allow air strikes to defend U.S.-trained Syrian rebels if they come under attack, even if those doing the attacking are Assad's forces.

The first known U.S. air strikes to support U.S.-trained rebels took place Friday when a group of forces came under fire from Nusra Front militants in northern Syria.

The Syrian civil war began in March 2011 and has killed more than 220,000 people and wounding at least 1 million, according to the United Nations.