Mohamed al-Bashir has been appointed caretaker prime minister of the transitional Syrian government until March 1, 2025, he said in a televised statement on Tuesday.

Al-Bashir ran the rebel-led Salvation Government before opposition fighters launched a 12-day lightning offensive, swept into Damascus and overthrew the Syrian regime.

The appointment was announced after the Israeli military pounded Syrian army bases on Tuesday with airstrikes as its troops reportedly advanced deeper into Syria.

Syrian security sources said the Israeli incursion reached about 25 kilometres southwest of Damascus, after Israel seized a buffer zone in southern Syria and launched airstrikes on Syrian army and air bases overnight.

Israel denied its forces had advanced into Syria beyond a buffer zone at the border, saying its aim is to keep weapons from falling into hostile hands.

A Syrian security source said Israeli troops reached Qatana, which is 10 kilometres into Syrian territory east of a demilitarized zone separating the Israeli-occupied Golan Heights from Syria.

Israel's military operation into Syria comes two days after the lightning overthrow of President Bashar al-Assad by a rebel alliance left Syrians, regional countries and world powers nervous about what comes next.

Lt.-Col. Nadav Shoshani, an Israeli military spokesperson, said troops remained in the buffer zone and "a few additional points" in the vicinity but he denied there had been any significant push into Syria beyond the separation area.

"IDF forces are not advancing towards Damascus. This is not something we are doing or pursuing in any way," he told a briefing with reporters.

Israel has said it will not become involved in conflict in Syria and that its seizure of the buffer zone was a defensive move.

Airstrikes wipe out Syrian army assets, sources say

Egypt, Qatar and Saudi Arabia have condemned the incursion. Saudi Arabia said the move would "ruin Syria's chances of restoring security."

Regional security sources and officers within the now fallen Syrian army said heavy Israeli airstrikes continued against military installations and airbases across Syria overnight, destroying dozens of helicopters and jets, as well as Republican Guard assets in and around Damascus.

The rough tally of 200 raids had left nothing of the Syrian army's assets, they said.

Israel said its airstrikes would carry on for days but told the UN Security Council that it was not intervening in Syria's conflict. It said it had taken "limited and temporary measures" solely to protect its security.

WATCH | Syrian prison the scene of desperate searches: 

Syrians search for loved ones as world watches what’s next

With the fall of Bashar al-Assad’s government, Syrians searched for those who went missing under his regime — especially in the country's notorious Sednaya prison. Meanwhile, the world waited to see what a new government could mean for the future.

The United Nations Security Council met behind closed doors late on Monday, and diplomats said they were still in shock at how quickly Assad's overthrow unfolded, after a 13-year civil war that was locked in stalemate for years.

"Everyone was taken by surprise, everyone, including the members of the council. So we have to wait and see and watch ... and evaluate how the situation will develop," Russian UN Ambassador Vassily Nebenzia told reporters after the meeting.

Mood in Damascus still celebratory

Russia played a major role in supporting Assad's government and helping it fight the rebels. The Syrian leader fled Damascus for Moscow on Sunday, ending more than 50 years of brutal rule by his family.

With the mood in Damascus still celebratory, Assad's prime minister, Mohammed Ghazi al-Jalali, on Monday agreed to hand power to the rebel-led Salvation Government, an administration based in rebel-held territory in northwest Syria.

The main rebel commander Ahmed al-Sharaa, better known as Abu Mohammed Al-Golani, met with Jalali and Vice-President Faisal Mekdad to discuss the transitional government, a source familiar with the discussions told Reuters. Jalali said the handover could take days to carry out.

Al Jazeera television reported the transitional authority would be headed by Mohamed al-Bashir, who has headed the Salvation Government.

The steamroller advance of the militia alliance headed by Hayat Tahrir al-Sham (HTS), a former al-Qaeda affiliate, was a generational turning point for the Middle East.

The civil war that began in 2011 killed hundreds of thousands, caused one of the biggest refugee crises of modern times and left cities bombed to rubble, the countryside depopulated and the economy hollowed out by global sanctions.

But the rebel alliance has not communicated plans for Syria's future, and there is no template for such a transition in the fractious region.