Washington deeply alarmed by the frequency of such attacks in recent months.
The US has condemned three terrorist attacks in northern Syria that killed at least 20 civilians.
"The United States condemns the terrorist attacks this past weekend in Azaz, Al Bab and Afrin that resulted in the deaths of at least 20 civilians, including children," said State Department Spokesperson Ned Price in a statement.
No group has claimed responsibility for the attacks, but local security personnel suspect the YPG/PKK terror group.
"The United States is deeply alarmed by the frequency of such attacks in recent months, including the repeated use of vehicle-borne improvised explosive devices," said the statement.
"Those responsible for perpetrating the violence should be brought to justice. Their actions endanger the Syrian people and threaten to destabilise the region further," it added.
YPG/PKK terrorists continue to carry out attacks, but do not claim responsibility when they end up harming civilians, according to local security sources.
The terror group, attacking from Syria’s adjacent Tal Rifaat and Manbij regions, often targets Jarabulus, Azaz, Afrin and Al Bab.
The YPG is the Syrian wing of PKK terror group.
US condemns a series of YPG terrorist attacks against civilians in Syria, without naming the perpetrators. https://t.co/E80cHNtWaf— Ragıp Soylu (@ragipsoylu) February 2, 2021
A car bomb exploded leaving at least five people dead and more than 25 injured in Northern Aleppo, Syria's al Watan newspaper reported on Sunday.
State news agency SANA reported the bombing in the city of Azaz but did not say how many people had been killed or injured.
A separate suicide car bombing at a checkpoint manned by the Turkish-backed Syrian National Army (SNA) in the Bezaa area, also in Northern Aleppo, killed six SNA members and injured four, sources said.
Turkey's Anadolu Agency said 10 people had died and 24 were injured in two attacks in Northern Syria on Sunday, adding that a car bomb had exploded in the centre of Azaz.
At least five others were killed and scores wounded when a car bomb detonated in the town of Afrin on Saturday, the Turkish defence ministry and local civil defence said.
The ministry said in a statement the bomb attack took place in an industrial site at the centre of the town and wounded 22 people, saying that the attack was carried out by YPG/PKK terror group.
The local civil defence said the death toll due to the bomb stood at six, including children.
In its more than 30-year terror campaign against Turkey, the PKK, listed as a terrorist organisation by Turkey, the US and the EU, has been responsible for the deaths of nearly 40,000 people, including women, children and infants.
Since 2016, Turkey has launched a trio of anti-terror operations across its border in northern Syria to prevent the formation of a terror corridor and to enable the peaceful settlement of residents: Euphrates Shield (2016), Olive Branch (2018) and Peace Spring (2019).