Turkish forces have begun the siege of the Syrian city of Afrin, nearly two months after launching an offensive in the region against the Kurdish People’s Protection Units (YPG), announced the military on Tuesday. The military said in a brief statement that the siege of Afrin, the main town in the enclave, had begun Monday. The forces also captured “areas of critical importance” in the region as of Monday, it added. Thousands of people had started to flee Afrin on Monday as the Turkish troops got closer to the town, heading toward nearby Syrian regime-controlled areas. Afrin city is home to around 350,000 people, the Syrian Observatory for Human Rights says. Turkey launched a military offensive into the border enclave on Jan. 20 to drive out YPG forces that it considers to be "terrorists" and an extension of Kurdish rebels fighting inside Turkey. Ankara has threatened to push further east to Manbij, where YPG troops are stationed. The Turkish foreign minister said on Tuesday that Turkey and the United States have reached an agreement on a plan to jointly station Turkish and US forces in Manbij. Washington has not confirmed any such plan — and a small contingent of US forces is already in Manbij. Hurriyet newspaper quoted Mevlut Cavusoglu as telling Turkish reporters during a visit to Moscow that the "YPG will leave Manbij, US and Turkish soldiers will joint ensure its security." Cavusoglu revealed that he and US Secretary of State Rex Tillerson would discuss the issue further when they meet in Washington on March 19.