Damascus. 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.

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," US President Joe Biden said, crediting action by the United States 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 US 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 spokesman 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.

The leader of Syria's biggest rebel faction, Abu Mohammed al-Golani, is poised to chart the country’s future. The former al-Qaida 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 US 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 US-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.

An online video purported to show rebels freeing dozens of women at the notorious Saydnaya prison, where rights groups say thousands were tortured and killed. At least one small child was seen among them.

“This happiness will not be completed until I can see my son out of prison and know where he is,” said one relative, Bassam Masr. "I have been searching for him for two hours. He has been detained for 13 years.”

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 added.