DAMASCUS, March 12 (Xinhua) -- The Turkish forces and allied Syrian rebels were 4 km northeast of the Kurdish-controlled Afrin city in northern Syria, a monitor group reported on Monday.

Four kilometers separate the Turkish forces and allied Syrian rebels from the northeastern rim of Afrin city and 6 km from its northern border, said the Syrian Observatory for Human Rights.

The Turkish military campaign succeeded in capturing three towns on Saturday, becoming thus in control of 221 towns and villages since the "Olive Branch" operation launched on Jan. 20, the Observatory said.

With this progress, a total of 35 percent of the villages and towns in the countryside of Afrin have been seized by the Turkish forces, said the Britain-based watchdog group.

The Observatory, which claimed it relies on a network of activists on ground, said the civilians in Afrin have been severely suffering from the ongoing military showdown in that large area in the northern countryside of Aleppo province near the Turkish border.

A day earlier, Turkish President Recep Tayyip Erdogan said Turkey's military forces have besieged Afrin and are ready to enter the city "at any moment."

"We have besieged Afrin. We can enter Afrin at any moment," Erdogan said as Turkish forces were just 6 km away from the city.

"Turkey will make sure the east of the Euphrates to the Iraqi border is cleansed of any terrorist groups after operations in Syria," he said.

Turkey's Foreign Minister Mevlut Cavusoglu said Thursday Turkish forces would complete the Afrin offensive by May and would carry out a joint operation against the Kurdistan Workers' Party (PKK) militants in Iraq with Baghdad.

Turkey launched the operation to wipe out the People's Protection Units (YPG), which Ankara considers as a terror group affiliated to the PKK, from northwestern Syria.