An explosives-laden vehicle detonated Friday in a busy neighbourhood of Qamishli, one of the main Kurdish towns in northeastern Syria, officials said.
The attack, which Kurdish officials said caused several casualties, came as Kurdish forces were trying to hold off a massive cross-border assault by Turkey and its proxies.
The Syrian Democratic Forces -- the autonomous Kurds' de facto army -- spoke of casualties while the Syrian Observatory for Human Rights also reported the explosion claimed several civilian victims.
Qamishli has been hit by several car bomb attacks in recent months, usually claimed by the Islamic State jihadist group.
IS has not controlled fixed positions in the area since an SDF-led operation eliminated the last bastion of the jihadist "caliphate" earlier this year.
But it has conducted regular deadly operations in remote areas with bomb attacks carried out by sleeper cells.
Analysts and officials have voiced fears that the White House's plans to pull out of northeastern Syria would create a vacuum that could lead to resurgence of IS.
A Kurdish official blamed the latest bomb attack on IS but no statement from the jihadist group claiming responsibility had yet been published.
Syrian television aired footage of fire raging from the site of the blast in central Qamishli, a town where security responsibility is shared between the Kurds and regime forces loyal to President Bashar al-Assad.