A car bomb killed 20 people in northern Syria Monday, authorities said, vowing to punish those behind the attack in an area where Kurdish-led forces and Turkey-backed factions have clashed for weeks.

Also on Monday, Syrian leader Ahmed al-Sharaa said organizing elections could take up to five years, the week after he was appointed interim president and less than two months after ousting Bashar al-Assad.

The second such car bomb attack in days in northern Syria's Manbij -- and the deadliest attack since Assad's ouster -- comes amid talks between the new authorities, who are close to Ankara, and the Kurdish-led, US-backed Syrian Democratic Forces (SDF) over the group's future.

"A treacherous terrorist bombing targeted civilians in Manbij city, killing 20 people," Syria's presidency said in a statement, without apportioning blame.

There was no immediate claim of responsibility for the attack, which the SDF also condemned.

"This crime will not pass without imposing the most severe of punishments on those responsible," said the presidency, vowing "to pursue and hold accountable" those involved.

Fighting in the Manbij area has raged despite efforts from SDF backer the United States to broker a ceasefire.

Turkey, which opposes the SDF, is due to host Sharaa on Tuesday for his second international visit since Assad was toppled.

Sharaa, who was in Saudi Arabia for a second day Monday, said in a pre-recorded television interview that "my estimate is that the period of time will be approximately between four and five years until the elections".

He said in the interview broadcast by a private Syrian channel that the vote's infrastructure "needs to be re-established, and this takes time".

Sharaa also pointed to the "technological tools that the state needs" to hold a census "in order to have correct and clear statistics", in a country where more than 500,000 people have been killed in almost 14 years of war.

Millions of others fled abroad.

"People have told me a lot, 'organize elections and the people will vote for you'," said Sharaa, adding: "For me, that's not important -- what is important is that the process be correct."

He also promised "a law regulating political parties", adding that Syria would be "a republic with a parliament and an executive government".

Sharaa last week was also tasked with forming an interim legislature and the Assad-era parliament was dissolved, along with the Baath party which ruled Syria for decades.

His planned visit to Turkey follows the trip to Saudi Arabia, where he met Crown Prince Mohammed bin Salman as war-ravaged Syria seeks reconstruction funds from wealthy Gulf countries.

He will meet Turkish President Recep Tayyip Erdogan to discuss "joint steps to be taken for economic recovery, sustainable stability and security", Fahrettin Altun, head of communications at the presidency, said on X.

Turkish-backed factions launched attacks on Kurdish-held areas in northern Syria at around the same time as the Islamist-led offensive that overthrew Assad, seizing the strategic Tal Rifaat and Manbij areas.

SDF leader Mazloum Abdi condemned Monday's attack in a post on X, saying that "those responsible must be held accountable".

White Helmets rescuers said women and children were among those killed in the car bombing that targeted agricultural workers on outskirts of Manbij city.

Turkey has threatened a military operation against the SDF unless it accepts Ankara's conditions for a "bloodless" transition after Assad's fall.

Syria's new authorities have called on the force to hand over its weapons and integrate into a new national army, rejecting demands for Kurdish self-rule.

In Monday's interview, Sharaa said the new authorities were "in negotiations" with the SDF.

"There are differences on certain details," he said, without elaborating, adding that "nobody wants secession in Syria".

Last month, Foreign Minister Asaad al-Shaibani said after talks in Ankara that Syria would never allow its territory to be used as a staging ground for threats against Turkey.

Turkey has mounted multiple operations against the SDF since 2016, and Erdogan had repeatedly threatened to seize Kurdish-held areas in the north like Manbij.

The SDF spearheaded the military campaign that ousted the Islamic State jihadist group from Syria in 2019. It controls much of the oil-producing northeast, where the Kurds have enjoyed de facto autonomy for more than a decade.

Turkey accuses the SDF's main component, the People's Protection Units (YPG), of being affiliated with the Kurdistan Workers' Party (PKK), which it considers a "terrorist" group.