"There are now 45 dead from last night's attacks in Hasakeh, as most of those who were in critical condition passed away," the Syrian Observatory for Human Rights said, after reporting 33 killed last night.
Two explosions struck as members of Syria's Kurdish minority celebrated on the eve of Nowruz, the Kurdish new year, in the northeastern city of Hasakeh.
There was no immediate claim of responsibility on Friday, but Rami Abdel Rahman of the Britain-based Observatory said.
According to him, the explosions were a few hundred metres (yards) apart from each other, with at least one of them caused by a suicide bomber inside a vehicle.
The Kurdish People's Protection Units (YPG) control Hasakeh city, but IS militants have launched attacks on towns nearby.
The jihadist offensive has sparked fierce clashes with Kurdish militia in the province, which is strategically located along Syria's borders with Iraq and Turkey.
UN chief Ban Ki-moon condemned the "heinous" attacks, while the commander of the Kurdish security forces, Joan Ibrahim, said "the crime that occurred today in Hasakeh will not pass without retribution."
The Islamic State group killed more than 100 people in 24 hours of violence throughout Syria, after leaving more than 70 regime forces dead in attacks on government checkpoints in the central provinces of Homs and Hama.

Latest News from World News Desk