Russia's President Vladimir Putin has said Russia would add more than 40 new intercontinental ballistic missiles to its nuclear arsenal this year, while a defence official accused Nato of provoking a new arms race.
Mr Putin made his announcement a day after Russian officials denounced a US plan to station tanks and heavy weapons in Nato states on Russia's border as the most aggressive US act since the Cold War.
"More than 40 new intercontinental ballistic missiles able to overcome even the most technically advanced anti-missile defence systems will be added to the make-up of the nuclear arsenal this year," Mr Putin, flanked by army officers, said in a speech to a military and arms fair.
Tension is high between Russia and the United States over the crisis in Ukraine and Washington, and Moscow has disagreements on a range of other issues.
Russian officials have warned that Moscow will retaliate if the United States carries out the plan to store heavy military equipment in eastern Europe, including in the Baltic states, that were once part of the Soviet Union.
"The feeling is that our colleagues from Nato countries are pushing us into an arms race," RIA news agency quoted Russian Deputy Defence Minister Anatoly Antonov as saying on the sidelines of the arms fair.
The 40 nuclear missiles that Mr Putin referred to yesterday are not additional missiles, but replacements for old ones, says the BBC's Sarah Rainsford in Moscow.
The new ones are more high-tech and capable of penetrating anti-missiles defences.
On Monday, the Pentagon revealed that it is poised to store battle tanks, infantry fighting vehicles and other heavy weapons for as many as 5,000 troops in several Baltic and Eastern European countries, to deter any possible further Russian aggression in Europe.
Citing US and allied officials, one newspaper said that if approved, the proposal would mark the first time since the Cold War that Washington has stationed heavy military equipment in the newer Nato member states in Eastern Europe that were once part of the Soviet sphere of influence.
The proposal, which seeks to reassure European allies in the wake of Russia's annexation of Ukraine's Crimea in March 2014, is expected to be approved by US defence secretary Ash Carter and the White House before a Nato defence ministers' meeting in Brussels this month.
In recent days, the level of sabre rattling has increased with the news from Washington that America is also on the verge of storing heavy weapons including tanks and infantry fighting vehicles in Poland,.
Tomasz Siemoniak, the Polish defence minister said he had discussed such US military deployments last month with Mr Carter.
The US military has been conducting massive drills with Nato allies in Eastern Europe amid regional alarm over Russia's role in the Ukraine conflict.
Russian officials said the plan could have "dangerous consequences".
According to the BBC, the rising tensions with the West have prompted Mr Putin to focus upon his country's nuclear arsenal.
This is in part a reflection of Russia's continuing conventional military weakness.
Moscow is in the midst of a significant modernisation of its strategic nuclear weapons with new ballistic missiles being deployed, more modern bombers, and new submarines being launched.
Over recent years, older, obsolete weapons have been withdrawn from service, so the size of Russia's overall arsenal has been shrinking.
However, this decline could soon come to an end, raising all sorts of questions for other nuclear powers.
What most alarms the West is the renewed emphasis in Russian rhetoric on nuclear rather than conventional forces.
Threats to deploy short-range nuclear weapons in Crimea have been accompanied by veiled warnings of nuclear targeting against Nato members who might host ballistic missile defences.
Meanwhile, in Moscow yesterday, a Russian state television reporter has broken ranks and apologised for taking part in "propaganda madness" after being sacked for criticising Mr Putin.
Konstantin Goldenzweig, the former Berlin correspondent of the NTV channel, lost his job after giving an interview to a German station in which he referred to the Russian president's "well-known cynicism" and suggested it was advantageous to the Kremlin that the war in eastern Ukraine was prolonged.
The journalist now says he is ashamed at having taken part in what he called Russia's "general propaganda madness" since the beginning last year of the war in Ukraine, where combined Russian and rebel forces are fighting government troops.
State television in Russia dominates broadcast media and produces highly politicised and biased reports, which often refer to Ukraine's government as the "Kiev junta".