Damascus, Syria - The government of Syrian President Bashar al-Assad has almost completely lost control of the southern part of the war-torn country as rebel forces close in on Damascus.

The government's troops have withdrawn from their positions in the southern provinces of Quneitra, Sweida, and Daraa, the Syrian Observatory for Human Rights reported.

The southern province of Daraa is now completely controlled by the rebel alliance led by Salafist group Hayat Tahrir al-Sham (HTS), after government forces retreated from security checkpoints and military outposts there, it added.

Advancing forces "have begun the final phase of encircling the capital," commander Hassan Abdel Ghani was quoted by AFP as saying, as the Syrian army reportedly began abandoning areas just outside of Damascus.

China China's Xi Jinping to send top-level envoy to attend Trump inauguration

The Syrian army denied these reports, although it confirmed the withdrawal from both Daraa – considered the cradle of the 2011 uprising against Assad's rule – and Sweida.

"Our forces operating in Daraa and Sweida carried out a redeployment and repositioning... after terrorist elements attacked the army's checkpoints and posts far apart," the military said in a statement carried by the official Syrian news agency SANA.

According to the observatory, Syrian forces withdrew from their positions in Quneitra on Saturday for the first time since Israel occupied the nearby Golan Heights in 1967.

Similarly, government workers and UN teams in villages near the ceasefire line bordering Golan have left, and the areas are almost empty, the monitor added.

The dramatic escalation in Syria comes after an Islamist coalition led by Hayat Tahrir al-Sham launched a surprise offensive late last month, capturing major city after major city and reigniting the country's civil war after years of deadlock.

Mexico Mexico's president suggests new name for the US after Trump's "Gulf of America" dig

The military escalation in Syria has prompted several countries to call on their citizens to leave the country.

The UN said Saturday it is withdrawing non-essential staff from Syria, while the US urged citizens to leave "while commercial options remain available."