Turkey sent military reinforcements into Idlib on Sunday, Syrian opposition sources said, despite a ceasefire last week that helped prevent direct armed confrontation between Ankara and Russia.
Limited fighting was also reported between Turkish and Russian proxies around separation lines roughly drawn in the deal on Thursday between presidents Recep Tayyip Erdogan and Vladimir Putin in Moscow.
But Russian and regime air bombing, which the Syrian Network for Human Rights said killed at least 300 civilians in Idlib in the past two months, has stopped, the sources said.
Continued ground military activity indicates the perpetual nature of the conflict in Syria and the scramble among foreign powers with troops in the country to hold on to or expand their territory.
A witness in the Syrian town of Atma on the Turkish border said hundreds of Turkish troops equipped with tanks, artillery, multiple-rocket launchers and mobile radar jamming units crossed into Idlib on Sunday.
"Four mechanised columns came in since the morning," the witness, who declined to be identified, told The National.
Pro-regime forces have been advancing in Syria since Russia's military intervention in late 2015. The advances have been mainly due to Russian air power and deals between Turkey and Moscow to carve out spheres of influence.
Through these deals, reached through negotiations known as the Astana process, Turkey had all but stopped supporting the opposition’s goal of removing President Bashar Al Assad and instead focused on rolling back gains by Kurdish militia supported by the United States.
But the understandings between Ankara and Moscow collapsed at the start of this year.
For the first time since the outbreak of the Syrian revolt in 2011, Turkey last month launched sustained air and ground strikes against the regime and allied Shiite militia supported by Iran, causing hundreds of casualties in loyalist ranks in a span of days.
Ankara also renewed support to rebel forces in Idlib, enabling them over the past few weeks to resist the regime’s advances along two major highways passing through the province.
Another source in Idlib said regime forces on Sunday entered and then withdrew under rebel fire from three villages near the Zawiya Mountain. Fighting was also reported in the west of Hama province adjoining Idlib.
Zawiya Mountain overlooks the the M5 highway linking Aleppo to Damascus and the M4 between Aleppo and the Mediterranean coast, home to two Russian military bases. Many of Mr Al Assad’s Alawite minority sect live in the area, having come from the Alawite Mountains overlooking the coast.
Turkey announced on Saturday that last week’s ceasefire agreement was holding, as the regime touted territorial advances implicitly recognised in the deal, saying the M5 highway was now open.
The agreement called for a cessation of hostilities from midnight on March 6 and a six-kilometre buffer zone on both sides of the M4 that Russian and Turkish forces are to patrol jointly from the middle of the month.
Most of Idlib falls under under “de-escalation zones” drawn up under Russian supervision in Astana in 2017. The deal between Russia, Turkey and Iran was supposed to halt fighting in places where the revolt had not been crushed, offering the possibility of sustained humanitarian relief and restoration of basic services.
But all of these zones, except for parts of Idlib, have since been captured by the regime and the Iranian-backed militias under Russian air cover.
The regime’s gains and scorched earth tactics resulted in mass displacement and forced transfers of Sunni populations, mainly into Idlib, raising it population to more than three million. Nearly a million people have been displaced since pro-Assad forces launched their offensive in December, most of them squeezed into a strip of territory along the Turkish border.
Lack of any regime indication that it would halt its attack raised Turkish concerns of another refugee exodus from Syria into its territory, despite having all but sealed its borders.