Turkey will open its southwestern border with Syria for 72 hours to allow Syrians fleeing the pro-government forces' assault free passage to Europe, Turkish official sources have told Middle East Eye.

The decision came after a security meeting chaired by Turkish President Recep Tayyip Erdogan in Ankara late on Thursday after 33 Turkish soldiers were killed in Syria's Idlib province.

A senior Turkish official said on Thursday that Syrian refugees headed towards Europe would not be stopped either on land or by sea.

Syrian rebels claim control of Idlib's Saraqeb as government forces fight back Read More »

The official said that Ankara would order police and border and sea patrols to stand down if they detected any Syrian refugees trying to cross into Europe.

Groups of Syrian refugees and migrants from other countries began heading to Turkey's borders with Greece and Bulgaria after the announcement was made.

Various Turkish refugee groups have also organised buses for Syrian refugees intending to head to Turkey's border with Europe.

The governor of Hatay province said that Turkish soldiers were killed in a Syrian government attack in Idlib, a province where forces loyal to President Bashar al-Assad have been staging an offensive against rebels since December.

Since then, about a million civilians have been displaced towards the Turkish border - more than half of them children - and hundreds have been killed in the onslaught.

Nato meeting

Turkey blamed Thursday's air strike on Syrian government forces, who are backed by Russia.

However, Russia's defence ministry was cited by the RIA news agency on Friday as saying that the Turkish troops had been hit by artillery fire from Syrian government forces who were trying to repel an offensive by Turkish-backed rebel forces.

Russia is sending two warships equipped with cruise missiles to the Mediterranean Sea towards the Syrian coast, the Interfax news agency cited Russia's Black Sea fleet as saying on Friday.

North Atlantic Treaty Organisation (NATO) ambassadors were meeting in Brussels on Friday at Turkey's request to hold consultations about developments in Syria, the alliance said.

Under article four of Nato’s founding Washington Treaty, any ally can request consultations whenever, in their opinion, their territorial integrity, political independence or security are threatened.

Migrants not allowed through

Turkey's Demiroren news agency said around 300 migrants, including women and children, had begun heading towards the borders between European Union countries Greece and Bulgaria and Turkey's Edirne province at around midnight on Thursday.

Syrians, Iranians, Iraqis, Pakistanis and Moroccans were among those in the group, it said.

It said migrants had also gathered in the western Turkish coastal district of Ayvacik in Canakkale province with the aim of travelling by boat to the Greek island of Lesbos.

Video footage of the migrants broadcast by pro-government Turkish television channels could also not immediately be verified.

Turkish broadcaster NTV showed scores of people walking through fields wearing backpacks and said the refugees had tried to cross the Kapikule border into Bulgaria, but were not allowed through.

It said the same group of migrants had then walked through fields to reach the Pazarkule border crossing into Greece, but it was unclear what happened to them thereafter.

Greece has tightened sea and land borders with Turkey after the overnight developments in Idlib, government sources told Reuters on Friday.

The sources, who declined to be identified, said Athens was also in contact with the European Union and Nato on the matter.

'Turkey is currently hitting all known regime targets'

The Turkish soldiers' deaths are the biggest number of fatalities suffered by Ankara's forces in a single day since it began deploying thousands of troops into Idlib in recent weeks in a bid to halt the military push by Assad's forces and their allies.

The latest incident means a total of 46 Turkish security personnel have been killed this month in Idlib.

Fahrettin Altun, Erdogan's communications director, said in a written statement that the Turkish government had decided in the meeting to retaliate against Assad's forces by land and by air.

"Turkey is currently hitting all known regime targets. What happened in Rwanda and Bosnia cannot be allowed to be repeated in Idlib," he said.

Attacks on Turkish forces have caused severe tensions between the Syrian government's key ally, Russia, and Turkey, which backs certain opposition groups in Idlib.

Erdogan had vowed to launch a military operation to push back Syrian government forces if they did not retreat from a line of Turkish observations posts by the end of February.

The nine-year war in Syria has devastated much of the country. An estimated half a million people have been killed and millions have been forced to live as refugees.

Turkey hosts the largest number of refugees in the world, having taken in some 3.7 million Syrians.

Erdogan has repeatedly threatened to open the gates for migrants to travel to Europe.

If it did so, it would reverse a pledge Turkey made to the EU in 2016 and could draw western powers into the standoff over Idlib.