NATO Secretary General Jens Stoltenberg said on Monday that the alliance excludes the possibility of introducing a "no-fly zone" over Ukraine, NBC News said.

"We have no intentions of moving into Ukraine neither on the ground or in the airspace," Stoltenberg said, answering a journalist's question about whether he could rule out the introduction of a "no-fly zone" by the alliance over Ukraine.

NATO now has a responsibility to ensure that this conflict "does not spiral out of control that escalates even further into concern for full-fledged war in Europe involving NATO allies," he said.