Russia's army on Tuesday began three days of nuclear weapons drills involving thousands of troops across the country, as Kyiv escalates its drone attacks and with President Vladimir Putin headed to China.

Throughout its more than four-year offensive in Ukraine, Moscow has flaunted its possession of nuclear weapons and repeatedly threatened to use them.

The drills also come months after the last nuclear arms pact between Russia and Washington broke down and amid a spate of comments from Putin touting the prowess of Moscow's nuclear forces.

"From May 19 to 21, 2026, the Armed Forces of the Russian Federation are conducting an exercise on the preparation and use of nuclear forces in the event of a threat of aggression," the defense ministry said.

The drills will involve more than 65,000 soldiers and 7,800 types of equipment and weapons, including more than 200 missile launchers, the defence ministry said. Aircraft, ships, submarines and nuclear submarines will all take part.

The ministry said it would also test-launch ballistic and cruise missiles.

The ending of the New START agreement with Washington in February formally released the world's two largest nuclear powers from a raft of restrictions.

Russia has vowed to take a "responsible" approach to strategic nuclear capability.

But Putin has also said that developing Russia's nuclear forces is an "absolute priority," and Moscow this month tested a new long-range missile capable of carrying nuclear warheads.

Moscow said the drills "also address issues related to the joint training and use of nuclear weapons deployed on the territory of the Republic of Belarus".

Russia has deployed a nuclear-capable missile, the Oreshnik, to its neighbouring ally, which borders NATO.

Ukraine's President Volodymyr Zelenskyy has in recent days accused Moscow of preparing a new offensive from Belarus and ordered his troops to reinforce his country's northern border.

Moscow announced the start of the drills hours before Putin was due in China for a two-day visit.