Troops and tanks amassing along the border with Syria in anticipation of a major offensive and ensuing refugee crisis.

Antakya, Turkey – Turkey continued to deploy troops and heavy weaponry to its southwestern border with Syria in anticipation of a major offensive by the Syrian government and its allies on opposition-held territory.

A Turkish military convoy arrived at a Turkish outpost near the town of Morek, in Syria’s northern Hama province, early on Thursday.

Al Jazeera also observed the arrival of a military plane that unloaded dozens of Turkish soldiers at the civilian airport in Hatay province, about 50km from the Turkish-Syrian border. It was not immediately clear whether the troops were heading across the border.

Turkey already hosts 3.5 million Syrian refugees and is fearful of another major influx if Syrian forces – backed by Russian airpower and allied militias – attack the last remaining stronghold of opposition fighters in Idlib province.

According to Metin Gurcan, a Turkish security expert, the border reinforcement was a defensive measure.

“If you look at the types of those weapons systems, I would say they are all for defensive purposes. So I don’t think Turkey has offensive intention and capability to militarily intervene in the Idlib conundrum,” he told Al Jazeera.

“This is sort of the preventive, defensive military buildup to manage the anticipated refugee flow because of this push of Russia-backed Syrian forces from the south.”

Nearly 40,000 people have already fled Idlib after Syrian-Russian air attacks intensified over the last two weeks. The UN estimates, in a worst-case scenario, about 900,000 civilians could flee Idlib if a full-scale ground offensive begins.

This big bird just landed in Hatay and unloaded a few dozen soldiers. #Idlib pic.twitter.com/2PxQmWyXmL — Mariya Petkova (@mkpetkova) September 13, 2018

Turkish officials have repeatedly warned Russia and the Syrian government against attacking Idlib, saying it would lead to another massive wave of refugees heading towards Turkey.

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Over the past week, Turkey has deployed reinforcements and expanded defensive structures at about a dozen observation points across opposition-held territories in Idlib, western Aleppo, and northern Hama provinces.

The outposts were established after a de-escalation agreement was reached between Turkey, Russia, and Iran in July 2017.

Areas in Deraa and Homs provinces and the suburb of Eastern Ghouta were also part of the de-escalation deal, but over the past few months, they have been captured by Syrian government forces backed by the Russian air force and pro-Iranian militias.

On September 7, a ceasefire proposed by Turkey was rejected by Russia and Iran during a summit among the three countries in Tehran.

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‘Siege warfare’

A confrontation between Turkish forces and those backing the Syrian government are “highly unlikely” if the offensive on Idlib goes forward, said Gurkan.

Russia continues to control Syria’s airspace, he noted, and Turkey is unlikely to initiate any military action there without Russian approval.

“I don’t expect a large-scale ground offensive [by Syrian forces]. It is going to a gradual, incremental siege warfare that could last maybe nine to 10 months,” said Gurkan.

He added Turkey was unlikely to withdraw its observation points manned by its troops if heavy fighting begins.

“These are Russia-endorsed observation posts, the prime objective of which is to prevent the expansion of pro-Iranian Shia militias from Aleppo to Idlib,” he said.

According to Gurkan, Russia also wants to limit Iranian influence in Syria and prevent it from spreading into Idlib province.

Follow Mariya Petkova on Twitter: @mkpetkova