Russian President Vladimir Putin oversaw a set of nuclear arms drills on Oct. 29, amid growing Western concerns he will escalate the ongoing Russia–Ukraine war.

The Kremlin announced Putin observed the Tuesday nuclear training drills, which included ballistic and cruise missile test launches.

The drills entailed tests of all three components of Russia’s nuclear triad. Russian land-based missile forces fired a Yars intercontinental ballistic missile from Plesetsk State Test Cosmodrome in western Russia to the Kura test site in Russia’s eastern Kamchatka region.

The nuclear-powered strategic missile submarine Novomoskovsk launched ballistic missiles in the Barents Sea in the Arctic Circle, while the nuclear-powered submarine Knyaz Oleg also conducted a launch from the Sea of Okhotsk off Russia’s Pacific Coastline.

Tu-95MS long-range bombers, representing the aerial component of Russia’s nuclear triad, also launched air-launched ballistic missiles during the Tuesday drills.

These are the second set of nuclear drills Moscow has held in the past two weeks. The Tuesday drills follow an Oct. 18 exercise in the Tver region, northwest of Moscow, involving a unit equipped with Yars intercontinental ballistic missiles capable of striking U.S. cities.

The threat of nuclear force has loomed over the past 2 1/2 years of fighting between Russia and Ukraine.

Speaking at a conference hosted by the Financial Times in September, CIA Director Bill Burns said he believed there was a genuine risk in the fall of 2022 that Russian forces might employ tactical nuclear weapons amid the fighting in Ukraine.

Ukrainian President Volodymyr Zelenskyy has repeatedly called on the United States and his other Western backers to grant Ukraine long-range weapons and permission to use them deep inside Russian territory. Moscow, in turn, has suggested it could lower the threshold for deploying its arsenal of nuclear weapons.

Last month, Russian Deputy Foreign Minister Sergei Ryabkov said Moscow has a “clear intent” to revise its nuclear posture in response to the gradually increasing Western support to Ukraine to repel Russian invasion forces. Last month, Putin also suggested Russia could employ nuclear arms in response to a mass assault on Russia with “strategic or tactical aircraft, cruise missiles, drones, hypersonic and other aircraft.”

Addressing the nuclear drills on Tuesday, Putin said nuclear force remains “an extreme, exceptional measure to ensure state security” but is also “a reliable guarantor” of Russian sovereignty and national security.

“Given the growing geopolitical tensions and the emergence of new external threats and risks, it is important to have modern strategic forces that are constantly ready for combat use,” the Russian president said Tuesday.

Putin vowed Russia would continue to modernize its nuclear forces.

The Oct. 18 and Oct. 29 nuclear drills also took place after North Korea reportedly sent potentially thousands of its troops to Russia and that they may fight alongside Russian forces against Ukraine.

At a press briefing, deputy Pentagon spokesman Sabrine Singh said the deployment of North Korean forces in the ongoing Russia–Ukraine war would represent a “further escalation” in the conflict.

Singh said the United States would not restrain Ukrainian forces from using U.S.-supplied weapons against North Korean soldiers.

“Today, I can confirm that North Korean troops have been sent to Russia, and that North Korean military units have been deployed to the Kursk region,” NATO Secretary-General Mark Rutte said in a statement.

Pyongyang denied early claims of North Korean troops in Russia. Moscow has yet to directly confirm the alleged North Korean troop deployment.

Putin did not deny the allegation when asked about it during an Oct. 24 press conference. He specifically mentioned a mutual defense article of Russia’s partnership deal with North Korea and that what “we do within the framework of this article is our business.”

Reuters contributed to this article.