Russia's prime minister accused NATO on Saturday of restarting the Cold War amid increased military maneuvers and troop deployments to countries neighboring Russia, moves the alliance's top official defended as a necessary response to aggression from Moscow.

Russian Prime Minister Dmitry Medvedev told a meeting of top defense officials, diplomats and national leaders that sanctions imposed after Russia's 2014 annexation of Crimea and new moves by NATO "only aggravate" tensions.

"NATO's policies related to Russia remain unfriendly and opaque - one could go so far as to say we have slid back to a new Cold War," Medvedev said. "On almost a daily basis, we're called one of the most terrible threats either to NATO as a whole, or Europe, or to the United States."

The comments came after NATO Secretary-General Jens Stoltenberg told the Munich Security Conference that "Russia's rhetoric, posture and exercises of its nuclear forces are aimed at intimidating its neighbors, undermining trust and stability in Europe."

Later, Stoltenberg told The Associated Press in an interview that all of NATO's moves had been made in response to Russian aggression.

"NATO does not seek confrontation and we do not want a new Cold War. But we had to respond to the Russian military buildup, which we have seen over several years," he said. "Not only a military buildup, but the fact that Russia is willing to use military power to change borders in Europe as they have done in Ukraine."

The annual conference in Munich is one known for frank talk among top officials.

Speaking after Medvedev, U.S. Secretary of State John Kerry fired back that Europe and the United States would continue to "stand up to Russia's repeated aggression" and noted that in addition to a joint focus on Ukraine, Washington plans to quadruple spending to help European security. That will allow the U.S. to maintain a division's worth of equipment in Europe and an additional combat brigade in Central and Eastern Europe.

NATO also announced this past week it would add new multinational reinforcements to beef up defenses of front-line alliance members most at risk from Russia.

"Those who claim our trans-Atlantic partnership is unraveling - or those who hope it might unravel - could not be more wrong," Kerry said.

Stoltenberg stressed the need for dialogue, but also defended NATO's move to strengthen defenses, including moving more troops and equipment to countries bordering Russia. He said at a summer summit in Warsaw he expects NATO members "to decide to further strengthen the alliance's defense and deterrence."

He told the AP it was also a positive "first step" that NATO members have mostly stopped cuts to their defense budgets and were working toward NATO's expectation that its members spend 2 percent of GDP on defense - a goal few meet.

"I think all politicians would prefer to spend money on education, health, infrastructure. But security doesn't come for free, and as tensions increase then we have to adapt," he said. "When tensions went down after the end of the Cold War there was a peace dividend and defense spending went down. But when tensions are increasing, then we have to again increase our defense investments."

Expressing the concerns of some Eastern European countries, Lithuanian President Dalia Grybauskaite told the conference that Moscow is already "demonstrating open military aggression in Ukraine, open military aggression in Syria."

"It's nothing about cold," she said, referring to Medvedev's Cold War comments. "It is already very hot."

Ukraine's President Petro Poroshenko blasted Russia's actions in both Ukraine and Syria, saying they are "a demonstration that we live in a completely different universe" from Russia.

He said the main danger to Europeans now is an "alternative Europe with alternative values" such as isolation, intolerance and disrespect for human rights. Poroshenko added: "This alternative Europe has its own leader. His name is Mr. Putin."

Stoltenberg, in his conference address, underlined that NATO's deterrent also included nuclear weapons, saying "no one should think that nuclear weapons can be used as part of a conventional conflict - it would change the nature of any conflict fundamentally."

Medvedev scoffed at what he said was a suggestion that Russia may use nuclear weapons in a first strike.

"Sometimes I wonder if it's 2016 or if we live in 1962," he said, referring to the year of the Cuban missile crisis.

Russian Foreign Minister Sergey Lavrov weighed in later, saying "it seems that old instincts are still viable."

"Clichés of ideological confrontation are returning into common use, the conceptual basis of which ceased to exist a quarter of a century ago," he said. "We need to agree on reforms of the world order, because such NATO-centered self-conceit, which reflects political short-sightedness, causes severe damage to the search for responses to common real challenges."

Medvedev also called for sanctions on Russia imposed after it annexed Crimea to be lifted, saying they are "a road that leads nowhere." He suggested the West would only harm itself if it did not lift the sanctions soon.

"The longer the sanctions continue, the more chances fade for Europeans to keep their positions in Russian markets as investors and suppliers," he said. "That's why one has to act quickly."

Kerry said if Russia wants an end to sanctions, it has the "simple choice" of fully implementing the Minsk peace accord agreed upon last year.

"Russia can prove by its actions that it will respect Ukraine's sovereignty, just as it insists on respect for its own," he said.