Turkey wants a secure strip of territory 10 km (6.2 miles) deep on the Syrian side of its border, including the town of Azaz, to prevent attempts to "change the demographic structure" of the area and for humanitarian purposes, Deputy Prime Minister Yalçın Akdoğan said on Wednesday.Assad forces backed by Russian air strikes have advanced towards the Turkish border in a major offensive in recent weeks. YPG fighters, regarded by Ankara as terrorists, have taken advantage of the violence to seize territory from Syrian rebels.Turkey has accused the YPG of pursuing "demographic change" in northern Syria by forcibly displacing Turkmen and Arab communities. "There is a game being played with the aim of changing the demographic structure. Turkey should not be part of this game," Akdoğan said in an interview on the AHaber television station."What we want is to create a secure strip, including Azaz, 10 km deep inside Syria and this zone should be free from clashes," he said.Azaz is the last rebel stronghold before the border with Turkey north of the Syrian city of Aleppo, part of what was, before the Assad offensive, a supply route from Turkey to the rebels fighting Assad.It has come under heavy assault in recent days, but Turkey has said it will not let the town fall into the hands of the Kurdish YPG militia.German Chancellor Angela Merkel had also said that she supports Ankara's proposal for a no-fly zone in northern Syria.Ankara has been requesting that the U.N. establish "safe zones" in Syria since 2012 but could not find the necessary international support.Turkey, home to more than 2.6 million Syrian refugees, has long pushed for the creation of a safe zone in northern Syria to protect displaced civilians, avoiding the need to bring them into Turkey.But the proposal has so far gained little traction with Washington or NATO allies who fear it would require an internationally patrolled no-fly zone which could put them in direct confrontation with Assad and his allies.Akdoğan said another 600,000 people could flee to the Turkish border if Aleppo falls to the Syrian army.