Six civilians were killed on Monday in three simultaneous bombings in the predominantly Kurdish northeastern Syrian city of Qamishli.
There was no immediate claim of responsibility for the attacks, which came after the ISIS group said it was responsible for the killing of a priest from the city.
Two car bombs and an explosives-rigged motorcycle blew up in a busy market and near a school and several churches, the Britain-based Syrian Observatory for Human Rights said.
Six civilians were killed and 22 wounded in the attacks, said the war monitor group, which relies on sources inside Syria for its reports.
An AFP correspondent saw charred cars and smoke rise from the site of the blasts which also destroyed shops and shattered windows in a three-storey building.
Syria's state news agency SANA confirmed the explosions were triggered by car bombs. It said two blasts went off in a commercial street while the third was near a hotel.
Firefighters tried to put out the flames caused by the explosions, as ambulances rushed to the scene and rescue workers carried away the victims.
Tow trucks removed the mangled remains of vehicles from the scene as security forces tried to keep passersby at bay.
The blasts came after ISIS claimed to have killed an Armenian Catholic priest from Qamishli.
The France-based association L'Oeuvre d'Orient which supports Christian minority communities in the region identified the priest as Father Joseph Hanna Ibrahim.
It denounced his killing along with that of his father as a "terrorist attack" and also condemned the three blasts that rocked Qamishli saying they took place "near churches".
The Observatory said the priest and his father were killed by gunfire as they made their way to the eastern province of Deir Ezzor to inspect the restoration of a church there.
Kurdish fighters led the US-backed battle against ISIS in Syria, expelling the extremists from the last scrap of their proto-state in March.
But the terrorists have continued to claim deadly attacks in northeastern and eastern Syria since then.
Qamishli has been hit by several car bombs in recent months, usually claimed by ISIS sleeper cells who continue to operate in the region.
On October 11, ISIS claimed responsibility for a bomb attack that killed at least six people in Qamishli. The victims included civilians and security forces, according to Kurdish officials.
In July, ISIS said it was responsible for a massive truck bomb that killed at least 44 people in Qamishli.
A Turkish cross-border attack against Kurdish fighters on October 9 heightened fears that ISIS fighters could break out in mass from Kurdish jails.
But a fragile Turkish-Russian ceasefire deal has more or less halted that offensive, and seen Kurdish forces withdraw from areas along the Turkish border, except Qamishli.