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 rebel alliance swept into the capital Damascus on Sunday, ending five decades of brutal rule by his clan.
Abu Mohammed al-Jolani, the 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 organization, 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.
Thousands missing
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.
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 UN 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 realized.
Concerns about sectarian violence have also surfaced, though HTS has sought to reassure religious minorities they will be safe in the new Syria.