The Assad regime is threatening a resumption of a deadly offensive against opposition-held northwest Syria.

A “senior Syrian field source” told the Russian State outlet Sputnik Arabic that the regime’s military has sent significant reinforcement to the frontlines in partitioned Idlib Province: “The Idlib offensive is just around the corner”.

Pro-opposition activists have also reported the buildup of pro-Assad forces in recent days, while a pro-Assad blog, Al Masdar, is boasting about an imminent offensive.

Russia and Turkey agreed a ceasefire on March 5, pausing an 11-month Russian-regime offensive that seized almost all of Hama Province and parts of southern and eastern Idlib. The attacks killed about 2,000 civilians, wounded thousands, and displaced more than a million.

The senior regime official assailed Turkey, whose forces entered northern Syria in August 2016: “It seems that the Turks are not serious in dealing with this matter, and they could not at least control the armed groups.”

The official specifically complained about challenges to control of the cross-Idlib M4 highway, seized by the offensive early this year.

Under the March 5 agreement, Russian and Turkish forces are supposed to patrol a 12-km (7.5-mile) wide corridor along the M4, but protests have prevented patrols for more than few kilometers along the highway.

There have also been clashes in the al-Ghab Plain at the junction of Idlib and Hama Provinces, and Russian warplanes have twice broken the ceasefire in the past two weeks.

On Sunday a meeting in Istanbul between the Russian and Turkish Foreign and Defense Ministers, also including regime supporter Iran, was abruptly cancelled.

Russian officials have not commented on the cancellation or the Assad regime’s threat to break the ceasefire.

In February, Turkish ground and air attacks checked the Russian-regime offensive with hundreds of ground and air strikes on Assad regime positions, following a regime attack that killed at least 36 Turkish troops.