BEIRUT — Syrian opposition fighters backed by Turkish airstrikes launched an offensive Saturday to try to capture Dabiq from the Islamic State group, which assigns special status to the northern Syrian town in its ideology and propaganda.

The Britain-based Syrian Observatory for Human Rights said the attack was preceded by intense shelling. It said Turkey-backed opposition fighters captured three villages, encircling Dabiq and cutting off all supply routes.

Turkey sent troops and tanks into northern Syria in August to help opposition forces recapture Islamic State strongholds and curb the advance of a US-backed Syrian Kurdish militia, which Ankara views as an extension of Turkey’s outlawed Kurdish separatists.

President Recep Tayyip Erdogan of Turkey, speaking in Rize on the Black Sea coast, said ‘‘we entered Jarablus, and then al-Rai, and now we are moving where? To Dabiq. We will declare a terror-free safe zone of 5,000 [square] kilometers.’’ He was referring to areas in Syria already captured by Turkish troops and Turkey-backed opposition forces.

Erdogan suggested that some of the nearly 3 million Syrian refugees in Turkey could return to newly liberated areas of their country. ‘‘They can go to their own lands. We can let them live there safely,’’ he said. ‘‘That’s the step we will take. We have given our proposal to coalition powers and we are moving together.’’

The town of Dabiq is central to Islamic State propaganda. The extremists, citing ancient prophecy, believe Dabiq will be the scene of an apocalyptic battle between Christianity and Islam. The group named its online magazine after the town, which it has occupied since August 2014.

But the extremist group, in its latest edition of its Nabaa online magazine, played down the importance of the looming battle, saying Turkey and its allies believe that Islamic State fighters don’t know the difference between ‘‘the lesser battle of Dabiq and the great Dabiq epic.’’

‘‘The great epic of Dabiq will be preceded by events that have signs of doomsday that the holy warriors in trenches know about,’’ al-Nabaa said.

The Observatory had reported that the extremists have been sending reinforcements into Dabiq over the past weeks, including one of their most elite units, known as Jaish al-Isra, which arrived in recent days. It also said Islamic State fighters have been planting mines and explosives.

Colonel Abdul-Razzaq Freiji, a Syrian officer who defected and now fights with the Turkey-allied forces, said his fighters are bombarding Dabiq and the nearby town of Soran in preparation for an all-out ground offensive.

‘‘Daesh members have gathered lots of fighters for this battle that will be harsh,’’ Freiji said by telephone from southern Turkey, using an Arabic acronym to refer to the group. ‘‘We are ready for the battle and we will take it [Dabiq] no matter what the price is, and after that we will march tow ard al-Bab,’’ he added, referring to one of the extremist group’s largest remaining strongholds in Syria.

To the west, a suspected Syrian or Russian air raid on the northern village of Termanin killed at least eight people.

The Observatory said the eight were killed when airstrikes targeted the center of the village and a checkpoint of the ultraconservative Ahrar al-Sham rebel group.

In the northern city of Aleppo, Syrian and Russian airstrikes hit several rebel-held eastern neighborhoods on Saturday amid clashes on the front lines in Syria’s largest city and onetime commercial center, according to the Observatory and the Aleppo Media Center, an activist collective.