ISTANBUL (Reuters) - The Turkish military has set up the sixth observation post in northern Syria’s Idlib province on Thursday as part of a de-escalation deal which it agreed with Iran and Russia, the army said.

It said the observation post was built in the Surman region at the southeast of Idlib, the deepest position Turkey’s armed forces have established so far inside northwest Syria.

Under the deal reached with Tehran and Moscow to try to reduce fighting between pro-government forces and mainly Islamist insurgents in the northwest Syria, Turkey agreed to set up 12 observation posts in Idlib and neighboring provinces.

That deal largely collapsed in December when the Syrian army along with Iran-backed militias and heavy Russian air power launched a major offensive to take territory in Idlib province and surrounding areas.

Turkey, which supported rebels trying to overthrow Syrian President Bashar al-Assad, has worked with Assad’s main international backers Russia and Iran in recent months to try to stem some of the bloodshed in Syria’s nearly seven-year-old civil war.