Ousted Syrian President Bashar al-Assad and his family have arrived in Moscow after being granted asylum in Russia, according to TASS, citing a Kremlin source.

"Assad and his family have arrived in Moscow. Russia, for humanitarian reasons, has granted them asylum," the Kremlin source said.

US President Joe Biden will address the extraordinary fall of the Assad regime in Syria in a speech tonight, the White House announced.

Biden is scheduled to speak in the Roosevelt Room, according to updated guidelines released by the White House. The president also received an update on the situation Sunday morning from his national security team.

It will mark Biden's first substantive remarks on the latest developments in the conflict, as US officials have been careful not to jump into the fray.

One of the main rebel groups leading the offensive, Hayat Tahrir al-Sham, or HTS, has been designated a terrorist organization by the US.

The Biden administration is keenly aware that the end of the Assad regime and what happens next could fundamentally reshape the balance of power in the Middle East. /CNN