Cold War warming up? Russia is considering arming its Baltic fleet with nuclear warheads for the first time since the cold war, the London-based Sunday Times has reported, quoting senior military sources.

The new Russian threat comes in response to the violent conflict in the Caucasus and a deal signed between the United States and Poland for a missile defense shield in Europe. Poland agreed on Thursday to host elements of a US global anti-missile system after Washington agreed to boost Warsaw's own air defenses.

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According to the report, under the Russian plans nuclear warheads could be supplied to submarines, cruisers and fighter bombers of the Baltic fleet based in Kaliningrad, a Russian enclave between Poland and Lithuania.

A senior military source in Moscow admitted that the fleet had suffered from underfunding since the collapse of communism, but told The Sunday Times that “that will change now."

"In view of America’s determination to set up a missile defense shield in Europe, the military is reviewing all its plans to give Washington an adequate response,” said the source.

'Russia's reaction is unfortunate'

According to the report, the proposal to bring back nuclear warheads was condemned by Kurt Volker, the US ambassador to Nato, who said he knew of the threat.

“It is really unfortunate that Russia chooses to react by putting nuclear warheads in different places – if indeed it does that – when the rest of the world is not looking at some kind of old-fashioned superpower conflict,” he said.

Russian President Dmitry Medvedev said on Friday that Washington's deal with Poland to shows the rocket shield is really directed against his country.

"This decision clearly demonstrates everything we have said recently," Medvedev said when asked about the agreement at a joint news conference with German Chancellor Angela Merkel in the Black Sea resort of Sochi.

A top Russian general said Friday that Poland's agreement to accept a US missile interceptor base exposes the ex-communist nation to attack, possibly by nuclear weapons, the Interfax news agency reported.

The statement by General Anatoly Nogovitsyn was the strongest threat that Russia has issued against the plans to put missile defense elements in former Soviet satellite nations.

"Poland, by deploying (the system) is exposing itself to a strike — 100%," Nogovitsyn, the deputy chief of staff, was quoted as saying.

He added, in clear reference to the agreement, that Russia's military doctrine sanctions the use of nuclear weapons "against the allies of countries having nuclear weapons if they in some way help them." That would include elements of strategic deterrence systems, he said, according to Interfax.