According to Ukrinform, Stoltenberg said this in a statement published on the website of the North Atlantic Alliance.
"I strongly condemn Russia's reckless and unprovoked attack on Ukraine, which puts at risk countless civilian lives. Once again, despite our repeated warnings and tireless efforts to engage in diplomacy, Russia has chosen the path of aggression against a sovereign and independent country," Stoltenberg said.
He noted that such actions by Russia are a grave breach of international law and pose a serious threat to Euro-Atlantic security.
"I call on Russia to cease its military action immediately and respect Ukraine's sovereignty and territorial integrity. NATO Allies will meet to address the consequences of Russia's aggressive actions. We stand with the people of Ukraine at this terrible time. NATO will do all it takes to protect and defend all Allies," Stoltenberg said.
Russia started a war against Ukraine at about 04:00 on February 24.