Three civilians were killed Friday when an explosives-laden vehicle detonated in a busy neighbourhood of Qamishli, one of the main Kurdish towns in northeastern Syria, officials said.
The attack, which wounded nine others, came as Kurdish forces pushed to hold off a massive cross-border assault by Turkey and its proxies.
"A car bomb targeted a restaurant at a time when civilians, including journalists who came to cover the offensive, were inside," the Kurdish internal security services known as Asayish said in a statement.
A video distributed by the Syrian Democratic Forces -- the autonomous Kurds' de facto army -- shows firemen trying to put out flames at the site of the blast, where at least five completely destroyed vehicles could be seen.
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 American troops out of northeastern Syria would create a vacuum that could spark an IS resurgence.
A Kurdish official blamed the latest bomb attack on IS but no statement from the jihadist group claiming responsibility had yet been published.
Security responsibility in Qamishli is shared between the Kurds and regime forces loyal to President Bashar al-Assad.