The Syrian army entered the northern city of Manbij for the first time in six years on Friday, after the Kurds, left exposed by a US pledge to pull out its own troops, asked for the regimes help to face a threatened Turkish offensive. A Syrian army spokesman said the national flag was raised in Manbij, a key city which lies about 30 kilometers south of the Turkish border. The Peoples Protection Units (YPG), which Turkey regards as a terrorist group and has vowed to crush, said its fighters had previously withdrawn from Manbij to fight ISIS militants in eastern Syria. "So we invite the Syrian government which we belong to... to send its armed forces to take over these positions and protect Manbij in the face of Turkish threats," the YPG statement said. It followed a shock announcement by its US ally last week of a full troop withdrawal from Syria. Russia welcomed the return of Kurdish territories in Syria to the control of the regime of Bashar Assad. "This is a positive trend," Kremlin spokesman Dmitry Peskov told a conference call.