The second such attack within days in Manbij comes amid talks between Syria's new authorities, which are close to Ankara, and the Kurdish-led Syrian Democratic Forces (SDF) over the group's future.

"A treacherous terrorist bombing targeted civilians in Manbij city, killing 20 people," the Syrian presidency said in a statement, following a preliminary death toll of 15 from rescuers.

There was no immediate claim of responsibility for the attack, which the SDF has also condemned, and the presidency statement did not say who may be behind it.

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

The 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 Syria's interim President Ahmed al-Sharaa on Tuesday for his second international visit since Bashar al-Assad's toppling on December 8.

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

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

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

The rescuers published footage from the area online, showing first responders carrying people on stretchers as well as the wreckage of a vehicle by the side of the road.

On Saturday, the Syrian Observatory for Human Rights war monitor said a car bomb in Manbij killed at least nine people including pro-Turkey fighters.