Aid trucks and ambulances entered Syria from Turkey on Sunday to deliver food and supplies to tens of thousands of people fleeing an escalating assault by regime forces on Aleppo, as air strikes targeted villages on the road north to the Turkish border.
Tens of thousands of Syrians have been fleeing to the Turkish border north of Aleppo since Thursday, following heavy Russian air strikes and reports of Syrian regime forces and its allies making gains in Aleppo's northern countryside, cutting opposition supply lines to Turkey.
Russia and Syrian regime forces intensified their campaign on opposition-held areas around Aleppo. Aid workers have said the city - Syria's largest before the war - could soon fall.
The Syrian regime forces and its allies were almost five km (3 miles) from the opposition-held town of Tal Rafaat, which has brought them to around 25 km (16 miles) from the Turkish border, said opposition members.
The Syrian Observatory for Human Rights, which monitors the war, said air strikes thought to be from Russian warplanes hit around the villages of Bashkoy, Haritan and Kfr Hamra north of Aleppo on Sunday, the latter two lying near the road to Turkey.
Russia's intervention has tipped the balance of the war in favour of Syrian regime leader Bashar al-Assad, reversing gains the opposition made last year. Advances by the Syrian regime forces and allied militant groups, including Iranian forces, are threatening to cut off opposition-held zones of Aleppo.
"In some parts of Aleppo the Assad regime has cut the north-south corridor ... Turkey is under threat," Turkish President Tayyip Erdogan was quoted by the Turkish local media as telling reporters on his plane back from a visit to Latin America.
Turkey's armed forces had the full authority to counter any threats to its national security, he said, although senior government officials have said the NATO member does not intend to mount any unilateral incursion into Syria.
Arab powers in the region including Saudi Arabia, and United Arab Emirates (UAE), which, like Turkey, want to see Assad removed from power, have expressed readiness to intervene with ground forces provided it is part of a co-ordinated international effort.
The UAE said on Sunday it was ready to send ground troops to Syria as part of an international coalition to fight against DAESH.
Saudi Arabia said last week it was ready to participate in any ground operations in Syria if the US-led coalition decided to start such operations.
Syria would resist any ground incursion into its territory and send the aggressors home "in coffins," the regime’s foreign minister said on Saturday, comments clearly aimed at the UAE and Saudi Arabia.
Iran, one of the main backers of the Syrian regime, responded to Saudi Arabia on Saturday by saying that the kingdom lacked the courage to go through with a plan to send ground troops to Syria and warned they would be wiped out if they went in.
Taking full control of Aleppo would be a huge strategic gain for the Assad regime in the five-year conflict that has killed at least 260,000 people across the country and driven 11 million from their homes. It could also push a massive new wave of refugees to the Turkish border.
Turkish border under pressure
Turkey has kept an open-door policy to civilians fleeing Syria throughout the conflict but is coming under growing pressure from Europe to stem the flow of migrants and from the United States to secure the border more tightly.
The country already sheltering nearly 2.7 million Syrians, the world's largest refugee population. But at the Oncupinar crossing in Turkey’s southern Kilis province, which has been largely shut for nearly a year, the newest arrivals were being shepherded into camps on the Syrian side.
"If those [refugees] have come to our door and they have no other choice and if needed we will let those brothers in, we have to do that," Erdogan was recently quoted as saying.
Aid officials at the Oncupinar border crossing said their efforts for now were focused on getting aid to the Syrian side of the border, where Turkish agencies have set up new shelters.
"We're extending our efforts inside Syria to supply shelter, food and medical assistance to people. We are already setting up another camp," an official from the Turkish Humanitarian Relief Foundation (IHH), which is funded by donations and carries out humanitarian work inside Turkey and abroad, told Reuters.
"At the moment all our preparations are to make sure these people are comfortable on the Syrian side of the border," the IHH representative added.
At a camp at Bab al Salama, inside Syria and across from Oncupinar, children played in the muddy lanes between rows of tents lashed by rain. Some were ripped and caked with mud, but others appeared to be newly set up.
A flag of the opposition Free Syrian Army fluttered over the road leading out towards the Syrian city of Azaz along which many of the displaced have travelled in recent days. Opposition fighters armed with Kalashnikovs wandered nearby.
Turkish Foreign Minister Mevlut Cavusoglu told reporters on Saturday that as many as 55,000 people are fleeing towards Turkey, as he left a meeting with EU foreign ministers in Amsterdam. Turkey's "open border" policy would be maintained, he said.