Islamist-led rebels toppled Syria's longtime ruler Bashar al-Assad in a lightning offensive that a U.N. envoy called "a watershed moment" for the nation marred by civil war.

German Foreign Minister Annalena Baerbock expressed understanding for the relief Syrian people felt after the fall of Bashar Assad’s government, but warned that “the country must not now fall into the hands of other radicals.”

“Several hundred thousand Syrians have been killed in the civil war, millions have fled,” Baerbock said in a statement emailed by her office Sunday. “Assad has murdered, tortured and used poison gas against his own people. He must finally be held accountable for this.”

Russia’s Foreign Ministry claimed Sunday that Bashar Assad had left Syria after negotiations with rebel groups, and gave “instructions” to “transfer power peacefully.”

In a post on the Telegram messaging app on Sunday, the ministry said Moscow had not directly participated in these talks. It also said it has been following the “dramatic events” in Syria “with extreme concern."

Iraqi embassy staff left Damascus on Sunday for neighboring Lebanon, a diplomatic source told AFP, after Syrian rebel forces seized the capital and declared the end of President Bashar al-Assad's rule.

U.S. President-elect Donald Trump posted on social media platform Truth Social Sunday, saying that "Assad has fled his country. His protector, Russia ... led by Vladimir Putin, was not interested in protecting him any longer."

He also wrote that Russia “lost all interest in Syria because of Ukraine, where close to 600,000 Russian soldiers lay wounded or dead."

Daniel B. Shapiro, a deputy assistant secretary of defense for the Middle East, said the U.S. presence was “solely to ensure the enduring defeat of ISIS and has nothing to do with other aspects of this conflict,” he said, using an acronym for the Islamic State group.

“We call on all parties in Syria to protect civilians, particularly those from Syria’s minority communities to respect international military norms and to work to achieve a resolution to include the political settlement,” Shapiro said.

Qatar’s foreign ministry spokesman and adviser to the prime minister, Majed bin Mohammed al-Ansari, says participants of the emergency meeting of foreign ministers and top officials from eight countries with interests in Syria, agreed on the need “to engage all parties on the ground and be inclusive in our engagement.”

The late Saturday meeting, hosted by Qatar, included Iran, Saudi Arabia, Russia and Turkey.

Syrian state TV briefly continued its programs, with an anchorman calling on all employees at the station to return to work adding that they are safe.

“This is Damascus, the capital of Syria where the gates of freedom have opened for the first time in many years. This is a historic day in Syria’s modern history” the anchorman said Sunday morning.

Crowds gathered in Syria's Damascus on Sunday to celebrate the fall of Bashar Assad’s government with chants, prayers and the occasional gunfire after opposition fighters entered the capital following a stunning advance.

Rami Abdurrahman of the Syrian Observatory for Human Rights, a Syrian opposition war monitor, said Assad took a flight from Damascus and left early Sunday. There was no immediate official statement from the Syrian government and Assad's whereabouts remain unknown.

Islamist-led rebels declared that they have taken Damascus in a lightning offensive on Sunday, sending President Bashar al-Assad fleeing and ending five decades of Baath rule in Syria.