U.S. National Security Advisor Jake Sullivan will travel to Israel this week for talks on Syria following the fall of Bashar al-Assad, and on a truce deal in Gaza, the White House said Monday.

Sullivan will meet Israeli officials to discuss "efforts to reach a hostage release and ceasefire deal in Gaza, the latest developments in Syria, and for discussions about Lebanon and Iran," National Security Council spokesman Sean Savett said.

Hundreds of Syrian refugees gathered at two border crossings in southern Turkey on Monday, eagerly anticipating their return home following the fall of President Bashar Assad's government.

Many arrived at the Cilvegozu and Oncupinar border gates at daybreak, draped in blankets and coats. Some camped by the barriers of the border crossing, warming themselves with makeshift fires or resting on the cold ground. The border crossings correspond to the Bab al-Hawa and Bab al-Salameh gates on the Syrian side of the border.

Across Lebanon, the Middle East, and beyond, the fall of Syria’s authoritarian government at the hands of Islamist-led rebels set off waves of jubilation, trepidation and alarm.

Many Lebanese exulted at the overthrow of the Syrian leader while others worried about more instability rocking a region in turmoil.

Israel's Foreign Minister Gideon Saar said Monday that his country's military takeover of the buffer zone along its border with Syria was a "limited and temporary step".

"This is a limited and temporary step we took for security reasons," Saar said in a press conference at the foreign ministry in Jerusalem. Israeli Prime Minister Benjamin Netanyahu announced on Sunday that he had ordered the army to "take control" of the zone after the fall of Syrian president Bashar Al-Assad.

Prime Minister Mohammed Ghazi Jalali, who remained in his post after Assad and most of his top officials vanished over the weekend, has sought to project normalcy.

“We are working so that the transitional period is quick and smooth,” he told Sky News Arabia TV on Monday, saying the security situation had already improved from the day before, when joyful crowds gathered in public squares and celebratory gunfire rang out across the capital.

A Syrian opposition war monitor says a top aide to the brother of Syria’s ousted president was found dead in his office near the capital, Damascus.

The Britain-based Syrian Observatory for Human Rights said Maj. Gen. Ali Mahmoud, who was in charge of Maher Assad’s office, had led a 2018 military campaign in southern Syria.

The Turkish-backed forces, known as the Syrian National Army, launched an offensive against the Syrian Democratic Forces in the northern Syrian city of Manbij on on Dec. 6, days after similarly expelling the SDF fighters from the city of Tal Rifaat.

Turkish security officials said Monday that “control of Manbij has been secured,” without providing further detail. The officials provided the information on condition of anonymity, in line with Turkish regulations.

The Israeli military said Monday that a drone that appeared to have originated in Yemen slammed into a city in central Israel.

Video posted by Israeli news sites showed a large burst of smoke erupting from a high-rise apartment building.

Abu Mohammed al-Golani, the militant leader whose stunning insurgency toppled Syria's President Bashar Assad, has spent years working to remake his public image, renouncing longtime ties to al-Qaida and depicting himself as a champion of pluralism and tolerance. As he entered Damascus behind his victorious fighters Sunday, he even dropped his nom de guerre and referred to himself with his real name, Ahmad al-Sharaa.

The extent of that transformation from jihadi extremist to would-be state builder is now put to the test.

Half a century of rule by the Assad family in Syria crumbled with astonishing speed after insurgents burst out of a rebel-held enclave and converged on the capital, Damascus, taking city after city in a matter of days.

Opposition forces swept across the country and entered Damascus with little or no resistance as the Syrian army melted away. President Bashar Assad, Syria's ruler for 24 years — succeeding his father, Hafez Assad — fled the country. Russian state media reported that he was in Moscow.