Russian President Vladimir Putin has ordered the Russian military to put its nuclear forces on special alert - the highest level of alert for Strategic Missile Forces.
Speaking to top military officials, including Defence Minister Sergei Shoigu, he said, Western nations had taken unfriendly actions towards Russia and imposed illegitimate sanctions.
Mr Putin had already issued a coded warning that he was willing to use nuclear weapons as he began his invasion of Ukraine.
Reacting over Russia's move, the US Ambassador to the United Nations, Linda Thomas-Greenfield, has called the move unacceptable.
In an interview with CBS News
she said , Russia's declaration means that President Putin is continuing to escalate this war in a manner that is totally unacceptable and they would continue to stem his actions in the strongest possible way.
Meanwhile, Ukrainian president Volodymyr Zelensky has released a statement following his conversation with Belarusian president Alexander Lukashenko today. President Zelenskyy said Kyiv will send a delegation for talks without preconditions with Moscow at the Ukraine-Belarus border, near the Pripyat River. Mr Zelensky had earlier said he would not meet a Russian delegation on Belarusian territory because Russia's invasion was launched in part from Belarus.