The world has plunged into a "new Cold War," the Russian premier said Saturday, as East-West tensions over Ukraine and Syria took center stage at a gathering of world leaders in Germany.

"We have slid into a new period of Cold War," Prime Minister Dmitry Medvedev told the audience at the Munich Security Conference.

"Almost every day we are accused of making new horrible threats either against NATO as a whole, against Europe or against the US or other countries," Medvedev added.

It did not take long for those accusations to resurface in Munich, as a group of leaders from Eastern Europe took the stage to criticize Russia's assertive foreign policy.

"Every single day, Russian troops, Russian weapons, Russian ammunition penetrate into my country," said Ukraine's President Petro Poroshenko.

He addressed Russia's president, who was not present, saying, "Mr Putin, this is not a civil war in Ukraine, this is your aggression. This is not a civil war in Crimea, this is your soldiers who occupied my country. This is not a civil war in Syria, this is your planes bombing the civilian population."

Poroshenko warned that "pro-Russian parties" are using alternative values to undermine Europe from within.

"Isolationism, intolerance, disrespect of human rights, religious fanatics, homophobia - this alternative Europe has a leader. His name is Mr Putin."

In contrast, Medvedev had previously criticized the expansion of NATO and EU influence deep into formerly Soviet-ruled Eastern Europe, which Russia still sees as part of its sphere of influence.

"European politicians thought that creating a so-called belt of friends at Europe's side, on the outskirts of the EU, could be a guarantee of security, and what's the result?" he said. "Not a belt of friends but a belt of exclusion."

But Medvedev also struck a more positive note, saying, "Our positions differ, but they do not differ as much as 40 years ago when a wall was standing in Europe."

He plead for more dialogue, citing the "shining example" of Pope Francis and Russian Patriarch Kirill's historic meeting in Cuba on Friday. NATO general secretary Jens Stoltenberg also addressed the forum, vowing a firm stance against Russia while boosting dialogue.

"Russia's rhetoric, posture and exercises of its nuclear forces are aimed at intimidating its neighbors, undermining trust and stability in Europe," Stoltenberg said in Munich.

"We have seen a more assertive Russia, a Russia which is destabilizing the European security order," he continued. "NATO does not seek confrontation, and we don't want a new Cold War. At the same time our response has to be firm."

Stoltenberg also noted that NATO is now "undertaking the biggest reinforcement to our collective defense in decades to send a powerful signal to deter any aggression or intimidation, not to wage war, but to prevent war."