LONDON — Syrian state media said Thursday that government forces were withdrawing from the city of Hama in the face of a rebel advance, marking another major setback for President Bashar al-Assad and his backers in Russia and Iran.

The Syrian Arab News Agency said government forces withdrew to positions outside the central Syrian city. The report came hours after opposition fighters — led by the Hayat Tahrir al-Sham group — claimed to have entered the city and struck towards its center.

Hama is Syria’s fourth largest city. It sits between the capital Damascus to the south and Aleppo — Syria’s second city — to the north. Aleppo fell to the lightning rebel offensive on Nov. 29. Hama was one of the few major cities that did not fall to anti-government forces following the 2011 revolution against Assad’s rule.

The Syrian army said its troops withdrew after rebel fighters broke through government defenses in Hama. The army accused the opposition groups of using suicide attacks to breach government lines.

The army’s General Command said the withdrawal was ordered to “preserve civilian lives” by avoiding fighting inside the city, SANA reported.

This is a developing story. Please check back for updates.

ABC News’ Someyah Malekian contributed to this report.