Turkey-backed rebels have largely taken control of the Syrian town of Al-Bab from Daesh militants, Turkish Prime Minister Binali Yildirim said on Tuesday. "Al-Bab has been largely taken under control. Our aim is to prevent the opening of corridors from territories controlled by terrorist organizations to Turkey," he said while speaking to members of his ruling AK Party in parliament. The Syrian rebels, backed by Turkish special forces, tanks and warplanes, swept into northern Syria in August in an operation, dubbed "Euphrates Shield" by Ankara, to push Daesh from Turkey's border and stop the advance of Kurdish fighters. The rebels have been pressing a major offensive on Al-Bab, 30 km (20 miles) south of the Turkish border for weeks. The advance risks putting them in direct conflict with Syrian government forces who are closing in on the city from the south. President Tayyip Erdogan and other Turkish leaders have been saying for weeks that the Al-Bab offensive was nearing an end. Meanwhile, Turkish security forces returned fire into Syrian territory controlled by a Kurdish militia on Monday and killed one member of the group, Turkey's armed forces said on Tuesday. It said the clash occurred at a border post in the Nusaybin area of Mardin province in southeast Turkey, across the border from an area controlled by the YPG militia. Ankara regards the Syrian group as closely tied to militants who have fought a three-decades-old conflict within Turkey.