Russian President Vladimir Putin has said the potential for conflict in the world and region has remained high, according to the RIA news agency.
The news agency said Putin gave the statement while remotely observing Russia’s annual exercise, called "Grom" or "Thunder", which involved nuclear submarines, strategic bombers and ballistic missiles.
According to Reuters, Russia rehearsed its response to a nuclear attack in the exercise at a time when tensions are high over a "dirty bomb" allegation it has made against Ukraine.
Russian officials said test launches of nuclear-capable ballistic and cruise missiles had passed off successfully.
The Pentagon said a day earlier that Russia had notified it of its intention to carry out the exercises at a time when NATO is rehearsing its own use of US nuclear bombs based in Europe in its annual "Steadfast Noon" war games.
The nuclear muscle flexing is sensitive because Russia is on the back foot in Ukraine and has accused Ukraine of planning to detonate a "dirty bomb" laced with radioactive material.
Kyiv and the West say there is no evidence for the allegation and that the warning looks designed to escalate tension around the war in Ukraine or to serve as the justification for some kind of Russian battlefield escalation.
Western officials have expressed fear that Moscow may be tempted to use a low-yield "tactical" nuclear weapon in Ukraine to try to force Kyiv to capitulate at a time when Ukrainian forces are advancing inside the Russian-occupied Kherson province, threatening a major defeat for Moscow.
US President Joe Biden warned Moscow on Tuesday that such a move would be an "incredibly serious mistake."
Putin, who will chair a Security Council meeting later on Wednesday, has warned that Russia has the right to defend its own territory using any weapons in its arsenal, which includes the world's largest nuclear stockpile, but has not specifically spoken of tactical nuclear weapons.