DAMASCUS: Syria"s foreign ministry on Monday slammed Turkey"s takeover of Afrin, demanding it "immediately" pull its forces from the northwestern city. Ankara and allied rebel groups captured the city from the Kurdish People"s Protection Units (YPG) on Sunday, after a two-month offensive on the broader Afrin region. The foreign ministry in Damascus sent two letters on Monday to the United Nations, protesting the capture as "illegitimate". "Syria condemns the Turkish occupation of Afrin and the crimes it is committing there, and demands the invading forces immediately withdraw from the Syrian territory they occupied," the ministry said in its letters, according to state news agency SANA. "Turkey"s behavior and attacks do not only threaten citizens and the unity of Syria"s land and people -- they also prolong the war on Syria," it added. Damascus has repeatedly criticised Turkey for its military operations on Syrian soil, accusing it of supporting "terrorist" groups. Pro-government militiamen even joined the fight to defend Afrin, dispatched from adjacent regime-held territory in Aleppo province. Turkey has killed dozens of them. The United States warned its NATO ally Turkey on Monday it is "deeply concerned" after a Turkish-led assault on the Syrian city of Afrin triggered an exodus of Kurdish civilians. "It appears the majority of the population of the city, which is predominantly Kurdish, evacuated under threat of attack from Turkish military forces and Turkish-backed opposition forces," State Department spokeswoman Heather Nauert said. "We are also concerned over reports of looting inside the city of Afrin. We have repeatedly expressed our serious concern to Turkish officials regarding the situation in Afrin," she said.