Crowds gathered in Syria's Damascus on Sunday to celebrate the fall of Bashar Assad’s government with chants, prayers and the occasional gunfire after opposition fighters entered the capital following a stunning advance.

Rami Abdurrahman of the Syrian Observatory for Human Rights, a Syrian opposition war monitor, said Assad took a flight from Damascus and left early Sunday. There was no immediate official statement from the Syrian government and Assad's whereabouts remain unknown.

Islamist-led rebels declared that they have taken Damascus in a lightning offensive on Sunday, sending President Bashar al-Assad fleeing and ending five decades of Baath rule in Syria.

Islamist-led rebels announced Sunday they had started entering the Syrian capital Damascus, where residents told AFP they heard heavy gunfire.

A war monitor said late Saturday that Islamist-led rebels had entered the strategic city of Homs, on the way towards Damascus where Syria's embattled government said it was setting up an impenetrable security cordon.

Iranian Foreign Minister Abbas Araghchi called for "political dialogue" between the Syrian government and opposition groups after a lightning offensive by rebel forces.

Turkey's foreign minister will meet with his Russian and Iranian counterparts in Doha on Saturday to try to find a solution to the renewed fighting in Syria and avoid chaos on its doorstep.

The three countries have been partners since 2017 in the Astana process seeking to end the civil war in Syria even if they have supported opposite sides on the battlefield.

The prime minister of Qatar says he has seen new momentum in Gaza ceasefire efforts since the U.S. presidential election, with the incoming Trump administration seeking an end to the conflict before it takes office.

Sheikh Mohammed bin Abdulrahman Al Thani, a key mediator in the ceasefire efforts, declined to give specifics of the negotiations but told an international conference in Doha that the gaps between the sides are not large.

Rebels on a lightning advance through Syria said on Saturday they have begun to encircle Damascus as government forces denied they had withdrawn from areas near the capital.

Syrian rebel commander Hassan Abdel Ghani sought to reassure religious minorities on Saturday after Islamist-led fighters snatched key cities and swathes of territory from government control.

Syrian opposition activists said insurgents have captured a main border crossing with Jordan forcing Syrian authorities to leave it.

Shortly afterward, Jordan’s Interior Minister al-Frayeh said the Naseeb border crossing with Syria had been closed because of the security situation on the Syrian side.