Assad has arrived in Russia after fleeing Syria

President Bashar Assad of Syria has arrived in Russia after fleeing his country, according to Russian state media and two Iranian officials, a stunning fall for the longtime dictator who lost his hold on power to a lightning fast offensive by rebels who took control of Damascus on Sunday.

The New York Times could not immediately independently confirm that Assad was in Russia, which along with Iran had helped keep him in power.

Assad's ouster was an earthshaking moment in the history of Syria, which the Assad family had ruled with an iron fist since the early 1970s. Rebel factions that have been trying to unseat him for more than a decade upended his government in a matter of days, after years of civil war.

Many in Syria greeted Assad's fall with hope after long living in fear of a government that had gassed its own people during the civil war and used oppressive tactics to silence dissent. But deep uncertainty over who will rule Syria next raised worries of a possible power vacuum in a country where competing factions have vied for territory against each other and Assad's forces.

"Our hearts are dancing with joy," Walaa Salameh, 35, a resident of the Damascus area, said in a phone interview. "We can't predict the future and anything is possible, but the most important thing is we got rid of this oppressive regime."

On Sunday, Abu Mohammed al-Golani, the Islamist rebel leader who spearheaded the rebel offensive, declared the group's achievement "a victory for the whole Islamic nation," speaking from the Umayyad Mosque, an ancient landmark in Damascus, the capital. His group, Hayat Tahrir al-Sham, once linked to al-Qaida, has tried to gain international legitimacy by eschewing jihadi ambitions and focusing on organized governance.

President Joe Biden, speaking from the White House, said that the United States would support the region "should any threat arrive from Syria during this period of transition," noting the terrorist roots of many of the rebels. But he underlined that Washington would engage with "all Syrian groups" to establish a transition "toward an independent, sovereign Syria."

Here's what else is happening:

-- Syria transition: As questions swirled early Sunday over Assad's whereabouts, Mohammed Ghazi Jalali, Syria's prime minister, said that he would stay in the country and was ready to work with whomever Syrians choose as their leader. Hayat Tahrir al-Sham said it would work with Jalali and called on Syrian military forces in Damascus to stay away from public institutions, which it said would remain under the prime minister's supervision until they are formally handed over.

-- Assad's allies: Assad had kept rebel forces at bay for more than a decade with Iranian and Russian military support. But in recent days, Iran and Russia appeared to be turning to diplomacy to preserve their interests in the country rather than significant military support. The Foreign Ministry of Iran said decision-making about the future of Syria was "solely the responsibility" of Syrians.

-- Prisoners freed: As the rebels advanced, they took over many of the notorious prisons where the Assad regime has for decades imprisoned, tortured and executed political prisoners. Videos emerging from north of Damascus show groups of men walking through city streets at night, reportedly after being freed from Sednaya prison, which the rebels have taken, according to war monitors and the fighters.

-- Broader instability: Israel's military said it had entered a demilitarized buffer zone in territory it controls in the Golan Heights, abutting Syria. The Israeli military, which is concerned about the sudden surge in instability near its borders, said it was acting to protect Israeli civilians. Iraq has secured its border with Syria, according to the official Iraqi News Agency, which said Sunday that al-Qaim border crossing was closed.