Turkey warned on Wednesday that pro-Syrian government forces entering the northwest Afrin region to support a Kurdish militia there will face “serious consequences” and they will be regarded as legitimate targets. A convoy of some 40-50 vehicles carrying pro-government forces tried to enter Syria’s Afrin on Tuesday, but retreated after artillery fire by Turkish forces, President Tayyip Erdogan’s spokesman said. The forces later resumed their progress and were in Afrin, media quoted regime sources as saying. “Any step by the regime or other elements in this direction will surely have serious consequences,” Ibrahim Kalin told a news conference, stressing Turkey’s determination to press ahead with its offensive to clear Afrin of Kurdish fighters despite an attempt by Syrian pro-government forces to enter the region. The Britain-based Syrian Observatory for Human Rights said Turkey’s offensive continued overnight, including shelling of the main Afrin town. Turkey launched a military operation last month to drive Kurdish YPG fighters out of Afrin. Ankara says the YPG is a terrorist group and an extension of the PKK which has fought a three-decade insurgency in southeast Turkey. “Any step there aimed at supporting the... YPG terrorist organization will mean they are directly siding with terrorist organizations and will therefore become legitimate targets for us,” Kalin said. Turkey launched its operation an air and ground offensive on Jan. 20 to clear Afrin of Syrian Kurdish fighters who it regards as "terrorists" because of their links to a Kurdish insurgency inside Turkey. However, on Tuesday the stakes were ratcheted up as hundreds of Syrian pro-government forces entered the region for the first time since 2012 to face off against Turkey alongside Kurdish forces. But they quickly came under shelling by Turkish forces, who said they had fired "warning shots" at the "pro-regime terrorist groups". In a statement, YPG spokesman Nuri Mahmud said the Kurdish forces had called on the regime forces to help fend off Turkeys assault. "The Syrian government responded to the invitation, answered the call of duty and sent military units today, February 20, to take up positions on the borders, and participate in defending the territorial unity of Syria and its borders," the statement said. The YPG has controlled Afrin since government forces withdrew from Kurdish-majority northern areas in 2012.