The rebels who ousted President Bashar al-Assad and are now in power in Syria appointed a transitional head of government Tuesday to run the country until March 1, a statement said.
"The general command has tasked us with running the transitional government until March 1," said a statement attributed to Mohammad al-Bashir on state television's Telegram account, referring to him as "the new Syrian prime minister".
Assad fled Syria as an Islamist-led rebel alliance swept into the capital Damascus on Sunday, ending five decades of brutal rule by his clan.
Abu Mohammed al-Jolani, the Islamist leader who headed the offensive that forced Assad out, had announced talks on a transfer of power and vowed to pursue former senior officials responsible for torture and war crimes.
His group, Hayat Tahrir al-Sham, is rooted in Syria's Al-Qaeda branch and is proscribed by many Western governments as a terrorist organisation, though it has sought to moderate its rhetoric.
The UN envoy for Syria said the groups that forced Assad to flee must transform their "good messages" into actions on the ground.
"They have been sending messages of unity, of inclusiveness," Geir Pedersen said, adding that in Aleppo and Hama, "we have also seen... reassuring things on the ground".But "what we need not to see is of course that the good statements and what we are seeing on the ground at the beginning, that this is not followed up in practice in the days and the weeks ahead of us."
The overthrow of Assad, who maintained a complex web of prisons and detention centres to keep Syrians from straying from the Baath party line, sparked celebrations around the country and in the diaspora around the world.
The civil war that led up to it killed 500,000 people and forced half the country to flee their homes, millions of them finding refuge abroad.
The country now faces profound uncertainty after the collapse of a government that had run every aspect of daily life.
Jolani, who now uses his real name Ahmed al-Sharaa, vowed: "We will not hesitate to hold accountable the criminals, murderers, security and army officers involved in torturing the Syrian people."
Jolani held talks on Monday with outgoing prime minister Mohammed al-Jalali "to coordinate a transfer of power that guarantees the provision of services" to Syria's people, according to a statement on Telegram.
The fall of Assad has sparked a frantic search by families of the tens of thousands of people held in his security services' jails and detention centres.
As they advanced towards Damascus, the rebels released thousands of detainees, but many more remain missing.
A large crowd gathered Monday outside Saydnaya jail, synonymous with the worst atrocities of Assad's rule, to search for relatives, many of whom had spent years in captivity there, AFP correspondents reported.
"I'm looking for my brother, who has been missing since 2013. We've looked everywhere for him, we think he's here, in Saydnaya," said 52-year-old Umm Walid."Since Bashar is gone, I'm optimistic. The fear is over."
Crowds of freed prisoners wandered the streets of Damascus, many maimed by torture, weakened by illness and emaciated by hunger.
Neighbouring Lebanon and Jordan welcomed home detainees who had been held in Syria for decades.
The United Nations said that whoever ended up in power in Syria must hold Assad and his lieutenants to account.
How the ousted leader might face justice remains unclear, but UN investigators who for years have been gathering evidence of horrific crimes called Assad's ouster a "game-changer" because they will now be able to access "the crime scene".
While Syrians were celebrating Assad's ouster, the country now faces enormous uncertainty, and it is unclear whether the dreams of democracy so many sacrificed their lives for will be realised.Concerns about sectarian violence have also surfaced, though HTS has sought to reassure religious minorities they will be safe in the new Syria.
Further complicating prospects, the Syrian Observatory for Human Rights said it had recorded more than 300 Israeli strikes on the country since Assad's fall.Pedersen, the UN special envoy for Syria, called on Israel to stop.
"We are continuing to see Israeli movements and bombardments into Syrian territory. This needs to stop. This is extremely important," he said.
AFP journalists in Damascus heard loud explosions on Tuesday but could not independently verify the source or scope of the attacks.
On Monday, Israel said it had struck "remaining chemical weapons or long-range missiles and rockets in order that they will not fall in the hands of extremists".
The Observatory, which relies on a network of sources around Syria, said Israeli strikes had "destroyed the most important military sites in Syria".
The group said the strikes targeted weapons depots, naval vessels and a research centre that Western governments suspected of having links to chemical weapons production.In the port city of Latakia, smoke was still rising Tuesday from the wreckage of naval vessels half under water in the harbour, an AFP correspondent reported.
Israeli Defence Minister Israel Katz confirmed that the military had been operating in Syria in recent days to "destroy strategic capabilities that threaten the State of Israel"."The navy operated last night to destroy the Syrian fleet with great success," he said.
Israel, which borders Syria, also sent troops into the UN-patrolled buffer zone east of the Israeli-annexed Golan Heights.
The defence minister said the military had orders to "establish a sterile defence zone free of weapons and terrorist threats in southern Syria, without a permanent Israeli presence."
Israel backer the United States said the incursion must be "temporary", after the United Nations said Israel was violating the 1974 armistice.
Assad spent years suppressing rebellion using everything in his means, including air strikes and even chemical weapons, but he was ultimately deposed in a lightning offensive that lasted less than two weeks.