BEIRUT - A car bomb exploded Saturday in a northern Syrian town controlled by Turkey-backed opposition fighters, killing at least 18 people and wounding several others, Syrian opposition activists and Turkey's Defense Ministry said.

Northern Syria has been hit by several explosions that have killed and wounded scores of people over the past month. That's since Turkey began a military operation against Kurdish fighters in the wake of President Donald Trump's decision to pull the bulk of American troops out of northern Syria.

The Britain-based Syrian Observatory for Human Rights reported that 19 people, including 13 civilians, were killed Saturday in the town of al-Bab in Aleppo province. The Aleppo Media Center, an activist collective, said 15 people were killed in the blast in a busy part of town near a bus station.

Turkey's Defense Ministry said the blast killed 18 people and blamed the main Kurdish militia, known as the People's Protection Units.

It is not uncommon for reports to give differing casualty figures in the immediate aftermath of this kind of attack.

No one claimed responsibility for the attack.

A video posted online by Albab City, an activist collective, showed several vehicles on fire with black smoke billowing from a wide street with shops on both sides. Inside the bus station, several white minibuses appear damaged.

"It looks like doomsday. May God help us," a man could be heard saying as five young men carried a wounded person away. At least two bloodied and wounded men could be seen rushed away on motorcycles.

Turkey-backed opposition fighters took control of parts of Aleppo province, including the towns of al-Bab and Afrin, in previous military offensives in 2016 and 2018, respectively.

The past month's attacks have come amid an expanding Turkish invasion of into northeast Syria against Kurdish-held towns and villages along a stretch of the border.

Three car bombs went off Monday in the northeastern Syrian town of Qamishli near the border with Turkey, killing at least six people, according to activists and Syria's state news agency SANA.

On Nov. 2, a car bomb killed 13 people in the northern Syrian town of Tal Abyad, which is also held by Turkey-backed opposition fighters.

The Turkish offensive has aimed at pushing Kurdish fighters away from the border. Those Kurdish fighters had been key U.S. allies in the fight against the Islamic State group. Turkey considers the Syrian Kurdish fighters terrorists linked to a Kurdish insurgency within Turkey.

Turkish forces have consolidated control over a stretch of the border running 120 kilometers (70 miles) wide and 30 kilometers (20 miles) deep into Syria. They have also kept up pressure outside that area, fighting with Kurdish forces on the edges.

Syrian government forces and their Russian allies have moved into other parts of the border under a Russian-Turkish deal.