Three simultaneous bombings killed at least six civilians in the Kurdish-majority city of Qamishli in northeastern Syria on Monday, a Kurdish security source and a Britain-based monitor said.
There was no immediate claim for the bombings, but they occurred shortly after the Islamic State group said it was responsible for the killing the same day of a priest from the same city.
In Qamishli, an AFP correspondent saw charred cars and smoke rise from the site of the blasts.
Firefighters tried to put out the flames caused by the explosions, as rescue workers carried away the victims.
The Syrian Observatory for Human Rights war monitor, which relies on sources inside Syria, said two car bombs and an explosives-rigged motorcycle blew up in a market and near a school in the city.
More than 20 people were wounded in the simultaneous attacks, said the Britain-based monitor said.
The blasts come after IS claimed to have killed an Armenian Catholic priest from Qamishli.
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 have led the US-backed battle against IS in Syria, expelling the extremists from the last scrap of their proto-state in March.
But the jihadists have continued to claim deadly attacks in northeastern and eastern Syria ever since.
In July, IS said it was responsible for a massive truck bomb that killed at least 44 people in Qamishli.