Syria's army command notified officers on Sunday that President Bashar al-Assad's 24-year authoritarian rule has ended, a Syrian officer who was informed of the move told Reuters, following a rapid rebel offensive that took the world by surprise.

Syrian rebels, who said Damascus was "now free of Assad", are expected to broadcast their first statement to the Syrian people on state television, two rebel sources said.

Assad, who had crushed all forms of dissent, flew out of Damascus for an unknown destination earlier on Sunday, two senior army officers told Reuters, as rebels said they had entered the capital with no sign of army deployments.

Thousands in cars and on foot congregated at a main square in Damascus waving and chanting "Freedom" from a half century of Assad family rule, witnesses said.

The dramatic collapse marks a seismic moment for the Middle East, ending the family's iron-fisted rule over Syria and dealing a massive blow to Russia and Iran, which have lost a key ally at the heart of the region.

"We celebrate with the Syrian people the news of freeing our prisoners and releasing their chains and announcing the end of the era of injustice in Sednaya prison," the rebels said, referring to a large military prison on the outskirts of Damascus where the Syrian government detained thousands.

A Syrian Air plane took off from Damascus airport around the time the capital was reported to have been taken by rebels, according to data from the Flightradar website.

The aircraft initially flew towards Syria's coastal region, a stronghold of Assad's Alawite sect, but then made an abrupt U-turn and flew in the opposite direction for a few minutes before disappearing off the map.

Reuters could not immediately ascertain who was on board.

The head of Syria's main opposition group abroad, Hadi al-Bahra Syrian, declared Damascus was now "without Bashar al-Assad".

As Syrians expressed joy, Prime Minister Mohammad Ghazi al-Jalali said he was ready to support the continuity of governance and prepared to cooperate with any leadership chosen by the Syrian people.

U.S. President Joe Biden and his team were monitoring the "extraordinary events in Syria" and were in touch with regional partners, the White House said.

The frontlines of Syria's complex civil war were dormant for years. Then Islamists once affiliated with Al Qaeda suddenly burst into action, posing the biggest challenge to Assad, who had survived years of gruelling war and international isolation with the help of Russia, Iran and Lebanon's Hezbollah.

But Assad's allies were focussed on and weakened by other crises, leaving Assad at the mercy of his opponents with an army that was not prepared to defend him.

Syrian rebel leader Ahmed al-Sharaa said on Sunday that it was prohibited to go near public institutions that he said will remain under the supervision of the "former prime minister" until they were officially handed over.

Israel, which has severely weakened the Iran-backed groups Hezbollah in Lebanon and Hamas in Gaza, will likely celebrate the fall of Assad, another of Iran's key regional allies. But the prospects of an Islamist group ruling Syria will likely raise concerns.

Just hours before reaching Damascus, rebels announced they had gained full control of the key city of Homs after only a day of fighting, leaving Assad's 24-year rule dangling by a thread.

Thousands of Homs residents poured onto the streets after the army withdrew from the central city, dancing and chanting "Assad is gone, Homs is free" and "Long live Syria and down with Bashar al-Assad".

The fall of Homs gave the insurgents control over Syria's strategic heartland and a key highway crossroads, severing Damascus from the coastal region that is the stronghold of Assad's Alawite sect and where his Russian allies have a naval base and air base.

Homs' capture is also a powerful symbol of the rebel movement's dramatic comeback in the 13-year-old conflict. Swathes of Homs were destroyed by gruelling siege warfare between the rebels and the army years ago. The fighting ground down the insurgents, who were forced out.

Hayat Tahrir al-Sham commander Abu Mohammed al-Golani, the main rebel leader, called the capture of Homs a historic moment and urged fighters not to harm "those who drop their arms".

Rebels freed thousands of detainees from the city prison. Security forces left in haste after burning their documents.

Syrian rebel commander Hassan Abdul Ghani said in a statement early Sunday that operations were ongoing to "completely liberate" the countryside around Damascus and rebel forces were looking toward the capital.

In one suburb, a statue of Assad's father, the late President Hafez al-Assad, was toppled and torn apart.

Outside the city, rebels swept across the entire southwest over 24 hours and established control.

EXISTENTIAL THREAT TO ASSAD RULE

The pace of events has stunned Arab capitals and raised fears of a new wave of regional instability.

Qatar, Saudi Arabia, Jordan, Egypt, Iraq, Iran, Turkey and Russia issued a joint statement saying the crisis was a dangerous development and calling for a political solution.

Syria's civil war, which erupted in 2011 as an uprising against Assad's rule, dragged in big outside powers, created space for jihadist militants to plot attacks around the world and sent millions of refugees into neighbouring states.

Hayat Tahrir al-Sham, the strongest rebel group, is the former al Qaeda affiliate in Syria regarded by the U.S. and others as a terrorist organisation, and many Syrians remain fearful it will impose draconian Islamist rule.

Golani has tried to reassure minorities that he will not interfere with them and the international community that he opposes Islamist attacks abroad. In Aleppo, which the rebels captured a week ago, there have not been reports of reprisals.

When asked on Saturday whether he believed Golani, Russian Foreign Minister Sergei Lavrov replied, "The proof of the pudding is in the eating".

ALLIES' ROLE IN SUPPORTING ASSAD

Assad's long rule relied on allies to subdue the rebels. Russian warplanes conducted bombing while Iran sent allied forces including Hezbollah and Iraqi militia to reinforce the Syrian military and storm insurgent strongholds.

But Russia has been focused on the war in Ukraine since 2022 and Hezbollah has suffered big losses in its own gruelling war with Israel, significantly limiting its ability or that of Iran to bolster Assad.

U.S. President-elect Donald Trump has said the U.S. should not be involved in the conflict and should "let it play out". (Text, excluding headline: Reuters)

Update news