Russia said it has serious grounds to believe the Turkish military is preparing to invade Syria, after peace talks collapsed under the advance of regime troops supported by Moscow. "The Russian Defence Ministry registers a growing number of signs of hidden preparation of the Turkish Armed Forces for active actions on the territory of Syria," said Russian Defence Ministry spokesman Major General Igor Konashenkov.

The claim was backed by satellite photos purportedly depicting an expansion of transportation infrastructure off a border checkpoint between Syria and Turkey. Before and after images taken in October 2015 and January 2016 showed the enlargement of a parking lot, which, Russia says, could be used for moving troops, ammunition and weapons.

"Such pads shown on images are used to support rapid movement of military convoys for logistic, operational deployment and evacuation purposes," the ministry tweeted. "Lots of such pads can be found along the Syrian-Turkish border, some of them with military hardware and personnel".

The supposed exposé came as Ankara's rivals in Syria are gaining the upper hand on the ground. This week, the Syrian military, backed by Russian airstrikes, made significant gains in Aleppo.

Regime forces managed to break a three-year siege of two western districts and were moving to encircle the key city that has been long split in government and opposition-held areas. The breakthrough followed days of heavy bombardments culminating four months of Russian airstrikes that have significantly shifted momentum in favour of Bashar al-Assad.

The pounding, which hit more than 500 targets according to monitoring groups, displaced thousands of people who fled towards Turkey, seeking refuge. Online footage showed columns of refugees marching away from the raging conflict.

In London for a conference on humanitarian aid to Syria, Turkey's Prime Minister Ahmet Davutoglu said 10,000 people were waiting to be allowed in at the border and 70,000 more were on their way. Meanwhile Kurdish militants were also reportedly gaining ground against in the Afrin area north of Aleppo.

The developments might force the Turkish governments' hand, analysts said.

The advance of regime troops in Aleppo also served as epitaph to UN-brokered peace talks in Geneva that broke down after just two days.