NATO Secretary General Jens Stoltenberg said Thursday that member state Turkey has a right to act in self-defense as the Turkish military operation in Syria's Afrin entered its sixth day.

"Turkey is one of the NATO nations that suffers the most from terrorism."

"All nations have the right to defend themselves, but this has to be done in a proportionate and measured way," Stoltenberg said in a statement issued by his office.

In addition, the Secretary General noted that NATO calls on the United States and Turkey to  start direct talks to resolve the problems around the Turkish operation against the Kurdish formations in Syria.