A suicide attack on a US military patrol in northern Syria has killed more than a dozen people, according to a war monitor.

The blast reportedly hit a busy restaurant in the centre of Manbij, a strategic city which is regularly patrolled by the US-led coalition.

The Syrian Observatory for Human Rights, a UK-based monitoring group, said two US soldiers were among the dead, but that claim could not be verified.

Isis claimed responsibility for the attack on its news site, Amaq, saying the perpetrator had used an explosive vest.

A spokesperson for the US-led coalition told The Independent that they were “aware of open source reports regarding an explosion in Syria.”

“Coalition forces conducted a routine patrol in Syria today. We are still gathering information and will share additional details at a later time,” they added.

Footage of the attack shared on social media shows an explosion on a busy street. There was no obvious presence of military forces. Local residents also shared video that appeared to show a US helicopter evacuating wounded from the site of the attack.

The attack comes less than a month after US president Donald Trump announced that American forces would be leaving Syria, and that Isis had been defeated.

The abrupt announcement caught officials within his own administration off-guard, and led to the resignation of defence secretary Jim Mattis.

Critics of the pull out argued that it could damage the fight against Isis, which was not yet over, and leave Washington’s Kurdish allies vulnerable to attack from Turkey.

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Manbij, where Wednesday’s attack took place, has been at the centre of a power struggle between those Kurdish allies and Turkey. The city is controlled by fighters linked to the Syrian Democratic Forces — a Kurdish-led militia that has fought alongside the US against Isis.

But Turkey views the group as terrorists, and had called for Kurdish fighters to leave the city. Following Mr Trump’s announcement that US forces would withdraw from Syria, the town has been bracing for a long-threatened Turkish incursion.