A car bomb killed three children near a village post office on Wednesday in northeast Syria, controlled by Kurdish forces who warn they face jihadist sleeper cells, local police said.
Police spokesman Ali Hassan described it as "a terrorist blast" that had sought to target a military vehicle.
Photos, which the police published, showed plumes of smoke rising from a building and from a car turned into charred, twisted metal.
In recent weeks, a series of attacks, including car bomb blasts, has hit towns and districts in northeast Syria under the control of the Kurdish YPG militia and its allies.
Two rigged motorcycles exploded a day before in Hasaka city, killing a 15 year-old-boy, police said.
Last month, Islamic State (IS) claimed a car bomb that injured eight people in front of a church in Qamishli city.
Syrian Kurdish leaders have warned of the risk sleeper cells pose after the US-backed Syrian Democratic Forces (SDF), which the YPG leads, defeated the last IS enclave in eastern Syria this year.
There was no immediate claim of responsibility for Wednesday's blast.