Forty-five people, including five children, were killed in attacks on Syrian Kurds as they celebrated their new year, a monitor said Saturday, accusing the Islamic State group of responsibility.
The attacks occurred Friday in what was one of IS's bloodiest days in Syria as the Sunni Muslim extremist group left dead more than 120 people across the war-ravaged country.
"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, updating its toll after reporting that 33 were killed.
Two explosions struck as members of Syria's Kurdish minority took part in festivities on the eve of Nowruz, the Kurdish new year, in the northeastern city of Hasakeh.
"They were lighting the candles at night, and there were a lot children around," said Observatory head Rami Abdel Rahman.
There was still no claim of responsibility, but Abdel Rahman told AFP that the Islamic State group was behind the attacks.
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.
Fear of additional attacks dimmed the spirit of the Nowruz celebrations in Hasakeh on Saturday.
"Today is supposed to be a day about freedom, but people were afraid of celebrating," Abdel Rahman said.
Hasakeh city is under the control of the Kurdish People's Protection Units (YPG) and regime forces, 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 IS jihadists also attacked government checkpoints and positions in the central provinces of Homs and Hama on Friday, killing at least 82 members of forces loyal to the Syrian regime.
Sixty-two of those deaths were in the province of Hama alone, where IS attacked regime points along a key road leading north to Aleppo.
In the southern province of Daraa, regime forces struck rebel-held neighbourhoods of the town of Busra al-Sham with at least 12 barrel bombs, the Observatory reported.
Barrel bombs are weapons crudely constructed of oil drums or other containers packed with explosives and usually dropped from helicopters.
The Observatory had no immediate report on death tolls, but human rights groups have criticised the use of barrel bombs for being indiscriminate and killing large numbers of civilians.