Syrian rebel fighters are launching a major military operation, backed by Turkish forces from inside Turkey, in a northern Syrian province largely controlled by jihadist militants, Turkish President Tayyip Erdogan said on Saturday.

The rebels said they were preparing to start the operation in Idlib soon, and residents reported Turkish authorities removing sections of a border wall.

“There’s a serious operation in Syria’s Idlib today and it will continue,” Erdogan said in a speech to his AK Party, adding that Turkey would not allow a “terror corridor” on its border with Syria.

“For now Free Syria Army is carrying out the operation there,” Erdogan said. “Russia will be protecting outside the borders (of the Idlib region) and we will handle inside,” he said.