Air strikes in the northern Syrian province of Idlib have killed at least 25 members of a prominent militant group formerly known as the Al-Nusra Front, activists say.

The British-based Syrian Observatory for Human Rights said on January 3 that it was unclear whether the attack against the Jabhat Fateh Al-Sham group had been carried out by aircraft belonging to Russia or to the U.S.-led coalition.

It said the dead included leading members of the group, which changed its name last year and announced it was splitting from Al-Qaeda.

Russia and Turkey say Jabhat Fateh al-Sham is not included in a cease-fire deal in Syria that Moscow and Ankara brokered last week.

Meanwhile, a number of rebel groups signed a statement saying they were halting preparations for peace talks planned for later this month in Kazakhstan.

The statement cited "breaches" in the cease-fire deal by the Syrian government and its allies as a reason.

Based on reporting by Reuters and AFP