(Bloomberg) -- President Vladimir Putin oversaw drills of Russia’s strategic nuclear forces, raising the stakes in a confrontation with the US and its allies over the war in Ukraine.

Ballistic and cruise missiles were fired during the exercises that involved nuclear forces on land, sea and air, according to a Kremlin statement late Wednesday. State television showed Putin being briefed on the drills by Defense Minister Sergei Shoigu.

Drills have been carried to test carrying out a “massive nuclear strike by strategic forces in response to enemy’s nuclear attack,” Shoigu told Putin in televised comments. 

Russia holds regular strategic drills toward the end of the year and this week’s tests took place as NATO conducted its annual nuclear exercises, Steadfast Noon, from Oct. 17-26.

Russia tested the Yars intercontinental ballistic missile in a launch from its Plesetsk cosmodrome in the western Arkhangelsk region to the country’s far eastern Kamchatka region, the Kremlin said. It also launched the Sineva ballistic missile from a nuclear submarine in the Barents Sea, and fired cruise missiles from Tu-95MS long-range bomber aircraft. 

The drills took place as fierce fighting continues in eastern and southern Ukraine, where its forces backed by billions in weapons from its US and North Atlantic Treaty Organization allies are striving to oust Russian troops from occupied territory in a war that’s lasted more than 600 days. 

Russian officials have repeatedly hinted that Moscow may resort to tactical nuclear weapons in the war, prompting condemnation from the US and NATO as well as warnings from China that this would be a red line for Beijing. 

Russia recently successfully tested a nuclear-powered missile called Burevestnik and has just brought into service the Sarmat, an advanced intercontinental nuclear ballistic missile, Putin said earlier this month.

The drills were announced as Russia’s upper house of parliament on Wednesday passed legislation to revoke ratification of the 1996 Comprehensive Nuclear Test Ban Treaty. 

Putin has said the move would put Russia on the same footing as the US, which signed but hasn’t ratified the accord. Neither side has conducted a nuclear test explosion since signing the treaty.

(Updates with details on regularity of drills)

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