Ukraine further said that Russia was holding Belarus as a "nuclear hostage". Belarus is among the closest Putin allies and also served as a staging ground for Russian forces invading Ukraine in February 2022.

Putin's announcement comes at a time when the West has stepped up its support to Ukraine. Poland and fellow North Atlantic Treaty Organization (NATO) member Slovakia have announced they would send MiG-29 fighter planes to Ukraine and United Kingdom announced last week to provide Ukraine with armour-piercing rounds containing depleted uranium.

What did Ukraine say?

Ukraine's government on Sunday called for an emergency meeting of the UN Security Council to "counter the Kremlin's nuclear blackmail" after Russian President Vladimir Putin revealed plans to station tactical atomic weapons in Belarus.

One Ukrainian official said Russia "took Belarus as a nuclear hostage".

Ukraine's Foreign Ministry condemned the move in a statement Sunday and demanded an emergency meeting of the UNSC.

"Ukraine expects effective action to counter the Kremlin's nuclear blackmail by the UK, China, the US and France," the statement read, saying these countries "have a special responsibility" regarding nuclear aggression.

"The world must be united against someone who endangers the future of human civilization," the statement said.

Oleksiy Danilov, the Secretary of Ukraine's National Security and Defence Council, tweeted Sunday that Putin's announcement was "a step towards internal destabilisation" of Belarus that maximised "the level of negative perception and public rejection" of Russia and Putin in Belarusian society. The Kremlin, Danilov added, "took Belarus as a nuclear hostage".

What did Putin say?

Russian President Vladimir Putin compared the stationing of Russian nuclear weapons in Belarus to US nuclear weapons in military bases in allied countries.?

However, the immediate reason cited by Putin for stationing nuclear weapons in Belarus was the UK's decision this week to provide Ukraine with armour-piercing rounds containing depleted uranium. He falsely claimed that the rounds have nuclear components.

Putin argued that by deploying its tactical nuclear weapons in Belarus, Russia was following the lead of the United States, noting that the US weapons are based in Belgium, Germany, Greece, Italy, the Netherlands, and Turkey.

He said, "We are doing what they have been doing for decades, stationing them in certain allied countries, preparing the launch platforms and training their crews. We are going to do the same thing."

Putin said Belarusian President Alexander Lukashenko has long asked for the nuclear weapons as a counter to NATO. He noted that Russia helped modernise Belarusian military aircraft last year to make them capable of carrying nuclear warheads. He said 10 such planes were ready to go. He said nuclear weapons also could be launched by the Iskander short-range missiles that Russia provided to Belarus last year.?

Other updates in Ukraine War

Further heightening tensions, an explosion deep inside Russia wounded three people on Sunday. Russian authorities blamed a Ukrainian drone for the blast, which damaged residential buildings in a town just 175 kilometers (110 miles) south of Moscow.

Ukraine has not commented on Sunday's explosion inside Russia. It left a crater about 15 metres (50 feet) in diameter and five metres deep (16 feet), according to media reports.

Russian state-run news agency Tass reported authorities identified the drone as a Ukrainian Tu-141. The Soviet-era drone was reintroduced in Ukraine in 2014, and has a range of about 1,000 kilometers (620 miles).

The explosion took place in the town of Kireyevsk in the Tula region, about 300 kilometers (180 miles) from the border with Ukraine. Russia's Defense Ministry said the drone crashed after an electronic jamming system disabled its navigation.

Similar drone attacks have been common during the war, although Ukraine hardly ever acknowledges responsibility. On Monday, Russia said Ukrainian drones attacked civilian facilities in the town of Dzhankoi in Russia-annexed Crimea. Ukraine's military said several Russian cruise missiles were destroyed, but did not specifically claim responsibility.

In December, the Russian military reported several Ukrainian drone attacks on long-range bomber bases deep inside Russia. The Russian Defence Ministry said the drones were shot down, but acknowledged that their debris damaged some aircraft and killed several servicemen.

Also, Russian authorities have reported attacks by small drones in the Bryansk and Belgorod regions on the border with Ukraine.

What are tactical nuclear weapons?

Tactical nuclear weapons are intended for use on the battlefield and have a short range and a low yield compared with much more powerful nuclear warheads fitted to long-range missiles. Russia plans to maintain control over the ones it sends to Belarus, and construction of storage facilities for them will be completed by July 1, Putin said.

Russia has stored its tactical nuclear weapons at dedicated depots on its territory, and moving part of the arsenal to a storage facility in Belarus would up the ante in the Ukrainian conflict by placing them closer to Russian aircraft and missiles already stationed there.

The United States said it would "monitor the implications" of Putin's announcement. So far, Washington hasn't seen "any indications Russia is preparing to use a nuclear weapon," National Security Council spokesperson Adrienne Watson said.

In Germany, the foreign ministry called it a "further attempt at nuclear intimidation", German news agency dpa reported late Saturday. The ministry went on to say that "the comparison drawn by President Putin to NATO's nuclear participation is misleading and cannot be used to justify the step announced by Russia".

(With AP inputs)