Syrian monitors say a suicide bomber and a car bomb killed 20 people and wounded 80 Friday during Nowruz celebrations in a northeastern Syrian city.
The British-based Syrian Observatory for Human Rights said most of the victims were Kurds welcoming the Persian new year in the city of al-Hasakah.
It blamed the two attacks on Islamic State, although no one has claimed responsibility so far.
Syria's state-run news agency said the attacks were carried out by "terrorists" — its word for the rebels fighting to overthrow President Bashar al-Assad.
The commander of Kurdish security forces in Syria wrote on Facebook that Friday's bombings "will not pass without retribution."