A truck carrying explosives has detonated in the western part of Qamishli, an area controlled by the Kurds.
Daesh has claimed the responsibility for the attack, local media report.
Earlier a source in the city's hospital told RIA Novosti that at least 25 people were killed and more than 100 injured.
"At least 25 bodies were transferred to the hospital. Over 100 people were injured; the death toll number will increase," the source said.
Horrible images from Al-Qamishli. Total number of dead and wounded keeps rising. Entire street destroyed. pic.twitter.com/QRCKFpxWuo— Leith Abou Fadel (@leithfadel) July 27, 2016
Some media reports suggested it was double blast.