The West is pushing Russia towards "a new Cold War" because of "unfriendly" policies, the country's prime minister has said.
Tensions rose between the West and Russia following the country's unilateral annexation of Crimea in early 2014. Russia's intervention in Syria, in support of President Bashar Assad, has also hurt relations with the West.
The Russian state was implicated in the killing of dissident Alexander Litvinenko in London in 2006 by a recent public inquiry.
But Dmitry Medvedev told a crucial gathering of politicians, diplomats and military personnel that Nato's policies towards Russia were to blame for frosty relations.
"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," he said told the Munich Security Conference on Saturday.
"Sometimes I wonder if it's 2016 or if we live in 1962," he added, referring to the year of the Cuban missile crisis, a highpoint in Cold War tensions.
He called for sanctions on Russia imposed after it annexed Crimea from Ukraine in March 2014 to be lifted, saying they were "a road that leads nowhere."
He said Vladimir Putin told the same conference in 2007 he was addressing that the West's building of a missile defence system risked restarting the Cold War, and that now "the picture is more grim; the developments since 2007 have been worse than anticipated."
But others blamed Russia's behaviour for the decline in relations, The Associated Press reports.
Nato Secretary General Jens Stoltenberg threw the blame back at Moscow. "Russia's rhetoric, posture and exercises of its nuclear forces are aimed at intimidating its neighbours, undermining trust and stability in Europe," he said.
Lithuanian President Dalia Grybauskaite said Russia "is demonstrating open military aggression in Ukraine, open military aggression in Syria."
"It's nothing about cold," she said. "It is already very hot."
The annual conference is one known for frank talk among top officials and participants this year include US Secretary of State John Kerry, French Prime Minister Manuel Valls, Ukrainian President Petro Poroshenko, Russian Foreign Minister Sergey Lavrov and Foreign Minister Philip Hammond.
Speaking after Medvedev, Kerry said 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 had quadrupled spending to help European security.
"Those who claim our trans-Atlantic partnership is unraveling - or those who hope it might unravel - could not be more wrong," Kerry said.
Medvedev's comments came shortly after Stoltenberg told the group that in response to a "more assertive Russia... which is destabilising the European security order," the alliance does "not want a new Cold War but at the same time our response has to be firm."
Stoltenberg stressed the need for dialogue but also defended Nato's move to strengthen defences, including moving more troops and equipment to countries bordering Russia, and said at an upcoming summer summit in Warsaw he expected member countries "to decide to further strengthen the alliance's defence and deterrence."
He 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.
Kerry also called upon Russia to strive for a peace deal in Syria, saying that its continued support of President Assad would just increase "the call to jihad" and complicate the fight against the so-called Islamic State.