Russia has taken Belarus as a "nuclear hostage," a top Ukrainian official said on Sunday.
President Vladimir Putin's move to station tactical nuclear weapons in Belarus is "a step towards the internal destabilization of the country," Oleksiy Danilov, head of Ukraine's National Security and Defense Council, warned in a tweet.
The decision "maximizes the level of negative perception and public rejection of Russia and Putin in Belarusian society," he said.
"The Kremlin took Belarus as a nuclear hostage," Danilov added.
Putin announced on Saturday that Russia will complete construction of a special storage facility for tactical nuclear weapons in neighboring neighboring Belarus, sparking concern and condemnation from Kyiv and its Western allies.
Putin said his counterpart Alexander Lukashenko had long raised the issue and Russia has agreed to "place tactical nuclear weapons in Belarus without violating the nonproliferation regime."
"The US has long placed such weapons in a number of countries, so there is nothing unusual in Belarus' request," the Russian leader said.
He said Russia has already handed over Iskander missile systems, which can be used to launch nuclear weapons, to Belarus.
Russia will have completed the construction of a storage facility for tactical nuclear weapons in Belarus by July 1 and the control of arms will not be transferred to Minsk, Putin added.