In the message broadcast Saturday on Al-Bayan radio, ISIS said it was behind explosions targeting Kurdish new year festivities in northeast Syria and raids on government positions in the central province of Hama.

Forty-five people, including at least 12 children, were killed in twin bombings in the northeastern city of Hassakeh Friday as they marked their new year’s eve, the Syrian Observatory for Human Rights said.

Observatory head Rami Abdel Rahman said people were too scared to celebrate on Saturday, fearing more attacks.

The ISIS radio station said the group detonated a car and a bike rigged with explosives in Hassakeh city, which is controlled by Kurdish fighters and Syrian regime forces.

The attacks, which took place on the bloodiest day in Syria so far this year, were widely condemned.

“Committing these barbaric crimes on this day, which amounts to a national holiday in Syria, shows that the killers have no link to the Syrian people or to their values. In fact, they lie in wait for Syrians,” said the Syrian National Council, the largest bloc in the opposition National Coalition.

“This description applies to the regime of [President Bashar] Assad and to the extremist terrorist organizations it has produced,” it said.

Syria’s foreign ministry sent letters to U.N. Secretary General Ban Ki-moon and the president of the U.N. Security Council calling for “steps to deter terrorist organisations and their funders.”

ISIS declared a “caliphate” in June 2014 that straddles large parts of Iraq and Syria under its control.

In its radio statement, the Sunni Muslim extremist group also claimed responsibility for a “special operation” Friday on a government supply route linking the provinces of Hama and Aleppo to the north.

“The soldiers of the caliphate stormed regime checkpoints,” Al-Bayan said, killing more than 100 regime soldiers and 15 fighters from Hezbollah, which has intervened in Syria on behalf of the government.

The Britain-based Observatory put the Hama death toll at 63, but said other ISIS attacks in the province of Homs had left 20 regime forces dead.

Syria’s conflict began in March 2011 with peaceful demonstrations but has since evolved into a bloody civil war increasingly dominated by the presence of jihadi groups.