Assad flees to Moscow after rebels take Syrian capital, Russian state ...

The latest:

• Biden calls government collapse an "act of justice," but warns of Mideast "uncertainty."
• Rebels promise a "free Syrian state" different from Assad's regime.
• Russia requested an emergency session of the UN Security Council.
• Israel says troops had seized a buffer zone in the Golan Heights .
• UN envoy urges urgent talks in Geneva to ensure "orderly political transition."

Ousted Syrian leader Bashar Assad fled to Moscow and received asylum from his longtime ally, Russian media said Sunday, hours after a stunning rebel advance seized control of Damascus and ended his family's 50 years of iron rule. 

Russian news agencies, citing a Kremlin source, reported on Sunday that Assad and his family have arrived in Moscow and have been granted asylum by Russian authorities.

The Interfax news agency quoted the unnamed source as saying asylum was granted "on humanitarian grounds." The Kremlin has not confirmed those reports.

Thousands of Syrians poured into streets echoing with celebratory gunfire and waved the revolutionary flag in scenes that recalled the early days of the Arab Spring uprising, before a brutal crackdown and the rise of an insurgency plunged the country into a nearly 14-year civil war.

The swiftly moving events raised questions about the future of the country and the wider region.

"Our approach has shifted the balance of power in the Middle East," U.S. President Joe Biden said, crediting action by the U.S. and its allies for weakening Syria's backers — Russia, Iran and Hezbollah.

He called the fall of Assad a "fundamental act of justice" but also a "moment of risk and uncertainty," and said rebel groups are "saying the right things now" but the U.S. would assess their actions.

Russia requested an emergency session of the UN Security Council to discuss Syria, according to Dmitry Polyansky, its deputy ambassador to the UN, in a post on Telegram.

The arrival of Assad and his family in Moscow was reported by Russian agencies Tass and RIA, citing an unidentified source at the Kremlin. A spokesperson there didn't immediately respond to questions. RIA also said Syrian insurgents had guaranteed the security of Russian military bases and diplomatic posts in Syria.

Earlier, Russia said Assad left Syria after negotiations with rebel groups and that he had given instructions to transfer power peacefully.

Rebels promise 'free Syrian state'

The leader of Syria's biggest rebel faction, Abu Mohammed al-Golani, is poised to chart the country's future. The former al-Qaeda commander cut ties with the group years ago and says he embraces pluralism and religious tolerance. His Hayat Tahrir al-Sham group, or HTS, is considered a terrorist organization by the U.S. and the UN.

In his first public appearance since fighters entered the Damascus suburbs Saturday, al-Golani visited the Umayyad Mosque and described Assad's fall as "a victory to the Islamic nation." Calling himself by his given name, Ahmad al-Sharaa, and not his nom de guerre, he said Assad had made Syria "a farm for Iran's greed."

The rebels face the daunting task of healing bitter divisions in a country ravaged by war and split among armed factions. Turkey-backed opposition fighters are battling U.S.-allied Kurdish forces in the north, and the Islamic State group is still active in remote areas.

Syrian state television broadcast a rebel statement saying Assad had been overthrown and all prisoners had been released. They urged people to preserve the institutions of "the free Syrian state," and announced a curfew in Damascus from 4 p.m. to 5 a.m.

'I haven't seen the sun until today'

Bashar Barhoum was one of those freed prisoners. 

Barhoum woke in his dungeon prison cell in Damascus at dawn Sunday, thinking it would be the last day of his life. The 63-year-old writer was supposed to have been executed after being imprisoned for seven months. 

He soon realized the men at the door weren't from Assad 's notorious security forces, ready to take him to his death. Instead, they were rebels coming to set him free. 

"I haven't seen the sun until today," Barhoum told The Associated Press after walking in disbelief through the streets of Damascus. "Instead of being dead tomorrow, thank God, he gave me a new lease of life."

Barhoum couldn't find his cellphone and belongings in the prison so set off to find a way to tell his wife and daughters that he's alive and well.

Videos shared widely across social media showed dozens of prisoners running in celebration after the insurgents released them, some barefoot and others wearing little clothing. One of them screams in celebration after he finds out that the government has fallen.

Rebel commander Anas Salkhadi appeared on state TV and sought to reassure religious and ethnic minorities, saying: "Syria is for everyone, no exceptions. Syria is for Druze, Sunnis, Alawites, and all sects."

"We will not deal with people the way the Assad family did," he said.

A person at Lebanon's border with Syria told CBC News on Sunday that he and his family have come to the crossing hoping to return to Syria.

Speaking through an interpreter, he said he and his family fled Syria eight years ago because "they are wanted [by] the regime."

'Like a dream'

Damascus residents prayed in mosques and celebrated in squares, calling, "God is great." People also chanted anti-Assad slogans and honked car horns. Teen boys picked up weapons that had apparently been discarded by security forces and fired them in the air.

Soldiers and police officers left their posts and fled, and looters broke into the Defence Ministry. Families wandered the presidential palace, walking by damaged portraits of Assad. Other parts of the capital were empty and shops were closed.

"It's like a dream. I need someone to wake me up," said opposition fighter Abu Laith, adding the rebels were welcomed in Damascus with "love."

Rebels stood guard at the Justice Ministry, where Judge Khitam Haddad said he and colleagues were protecting documents. Outside, residents sought information about relatives who disappeared under Assad.

Syria's historically pro-government newspaper al-Watan called it "a new page for Syria. We thank God for not shedding more blood." It added that media workers should not be blamed for publishing past government statements ordered from above.

A statement from the Alawite sect — to which Assad belongs and which has formed the core of his base