Thousands of Syrian refugees have fled the city of Aleppo to escape major military offensive, moving closer to Turkey.
A Turkish official said Saturday that as many as 35,000 Syrians had massed along the closed border.
The battle for Aleppo has escalated since UN-led efforts to begin peace talks in Geneva stalled last Wednesday, with facilitators suspending the process for three weeks.
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Suleyman Tapsiz, governor of the border province of Kilis, said Turkey would send aid to the displaced, such as food and shelter, but had no immediate plans to let them in. He said Turkey was prepared to open the gates in the event of an "extraordinary crisis."
The refugees have gathered at the closed Bab al-Salam border crossing with Turkey, travelling 50 kilometres.
"This is a major strategic city. Basically if the Syrian army succeeds in Aleppo, this would be a shattering blow, it would represent a major strategic defeat of the rebels," Fawaz Gerges of the London School of Economics, one of the world's foremost Middle Eastern scholars, told CBC News.
"You have one million residents in Aleppo, 500,000 in the government-controlled part of the city and 500,000 in the opposition dominated part of the city," Gerges said. "You've seen the tip of the iceberg. If the city is encircled, you're going to see 200,000 people trying to escape."
He added that he expects Turkey, currently home to two million Syrians displaced by the five-year war, will eventually reopen the border to more refugees.
"My take on it, is that the Turkish leadership is using this particular crisis to exert pressure on the western powers and United States. They want to show that the Russian military has aggravated the situation, that Russia is responsible for the new wave of refugees and they're putting pressure on Europe and the United States."
NATO has accused Russia of undermining efforts to find a political solution to the conflict in Syria by carrying out airstrikes, which the alliance says are mainly targeting opposition groups.
Syrian refugee Abdulkerim Hannura told Reuters that Russian planes have been carrying out airstrikes for the past 15 days on Syria's "northern countryside in general." He said there had been strikes on the towns of Sedef and Izzel, "on medical spots, on civilian homes."
"They concentrated there in a way that has led to people fleeing further north," he said.
Syria's foreign minister on Saturday said any foreign intervention in the conflict involving ground troops — without the agreement of his government — will be considered an "act aggression"
Walid al-Moualem said his country will resist any ground incursion into its territory and send the aggressors home "in coffins."