The Syrian National Army (SNA) has liberated northern Syrian town of Manbij from the U.S.-backed PKK/YPG terrorist group, clearing out the largest terrorist stronghold to the west of the Euphrates River, a Turkish security source said Monday.

A video, verified by Reuters, showed opposition forces being welcomed by people in Manbij, which is some 30 km (19 miles) south of the Turkish border.

Anadolu Agency (AA) said the SNA was searching for possible landmines and other traps left behind by terrorists in Manbij, a strategically key town for the terrorist group’s plans to create a terror corridor that would run from the Syrian-Iraqi border to the Mediterranean Sea on Syria’s western coast.

Syrian Interim Government President Abdurrahman Mustafa congratulated the people of Manbij and the SNA for liberating the town from PKK/YPG, calling it a "new step in re-facilitating Syria’s sovereignty".

The SNA launched Operation Dawn of Freedom to weed out the terrorist group from territories it seized in northeastern Syria. Tal Rifaat was liberated from terrorists in late November.

The SNA has been advancing through northern and western parts of Manbij, entering the central town Sunday, which has been occupied by the terrorists since 2016.

Residents of Manbij have joined the efforts, rising up against the terror group and rescuing prisoners held in local jails. The district's population is overwhelmingly Arab. Earlier in the operation, the SNA captured the town of Orayma and the village of Awn al-Dadat from the terrorists.

Launched on Dec. 1, Operation Dawn of Freedom began with the SNA clearing the Tal Rifaat district center of PKK/YPG terrorists. The operation aims to reclaim territory in northern Syria and restore security to the region.

Despite the promises of the U.S. and Russia, the PKK/YPG terrorists seized the Manbij district as a result of an attack launched with the support of the U.S. between May and August 2016. The U.S. had promised Türkiye that the PKK/YPG terrorists would leave the district after the area was cleared of the Daesh terrorists, but it did not fulfill this promise.

Moscow also undertook efforts to remove the terrorist organization from Manbij in an agreement reached with Ankara during Türkiye's Operation Peace Spring in October 2019 and announced that the terrorists had left – but the terrorist organization did not leave.

The Manbij region was of central importance in the PKK/YPG's plan to open a terror corridor starting from the Syria-Iraq border and reaching the Mediterranean in western Syria. Türkiye had already dealt a blow to preparations to establish a direct connection between Afrin, Tal Rifaat and Manbij with Operation Euphrates Shield in August 2016.

Amid setbacks for the Assad regime since the reignition of the conflict in Syria, the PKK/YPG has been seeking to exploit the unclear security situation. In recent years Türkiye has deployed troops and worked with local allies such as the opposition SNA to prevent this and keep locals safe from terrorist oppression.

The United States said it will maintain its presence in eastern Syria, where the PKK/YPG is concentrated, and will take necessary steps to "prevent a resurgence of Daesh," an official said Monday.

The United States is estimated to have 900 troops in eastern Syria as a hedge against Daesh terrorists.

Separately, U.S. Defense Secretary Lloyd Austin said U.S. strikes in Syria in recent days were focused on Daesh cells to hinder them from taking advantage of the fallout from the regime's collapse.