Russian warplanes have carried out the first air strikes in three months on the last remaining rebel stronghold in northwestern Syria, opposition activists have said.
There was no immediate word on any casualties following Wednesday's attacks.
It is believed the strikes on and near Idlib province were the first to be conducted by Russian planes since a truce in early March.
The ceasefire, brokered by Turkey and Russia, stopped a three month air and ground campaign that killed hundreds and sent one million people fleeing towards the Turkish border.
Russia is a main backer of Syrian President Bashar Assad’s forces, while Turkey supports the opposition.
Oppositionists said both Turkey and the Syrian government had been sending reinforcements to the region in recent days.
There have also been repeated violations of the truce on the ground in recent weeks.
The UK-based Syrian Observatory for Human Rights, an opposition war monitoring group, said Russian aircraft targeted rebel-held areas just south of Idlib province late Tuesday and Wednesday morning.
It also had no immediate word on casualties in the four airstrikes.
Syria has been locked in a civil war since 2011.