Turkish military shells Syrian Kurdish YPG positions: source

ANKARA (Reuters) - Turkey's military shelled positions of the Kurdish YPG militia in northern Syria on Thursday in response to cross-border fire, a Turkish security source said. Turkey has repeatedly shelled YPG positions in recent days, in response to the insurgents' advance in northern Syria near its borders. Turkey considers the YPG a terrorist organization, causing friction with NATO ally Washington, which backs the group in the fight against Islamic State in Syria. Turkish President Tayyip Erdogan said earlier the YPG's political wing was behind the deadly bombing in Ankara on Wednesday that killed 28 people. The head of the YPG's political arm has denied his organization's involvement in the attack. (Reporting by Orhan Coskun; Writing by David Dolan, Editing by Nick Tattersall)