Ukrainian President Volodymyr Zelenskyy on Sunday marked the country's Independence Day with a speech in Kyiv, stating that Ukraine would continue to fight for "a just peace," Ukrainian news outlet The Kyiv Independent posted.

His remarks came after Russian officials said Ukraine had launched a drone attack on Russia's Kursk nuclear plant on Sunday, forcing a sharp fall in the capacity of a reactor at one of Russia's biggest nuclear power plants and sparking a huge blaze at the major Ust-Luga fuel export terminal. The attacks create a threat to nuclear safety, the regional acting governor Alexander Khinshtein responded.

Canadian Prime Minister Mark Carney and U.S. President Donald Trump's envoy Keith Kellogg attended the Independence Day celebrations. Trump wrote in his letter to Ukraine that the United States believes in Ukraine's future as an independent state, CNN reported.

Russian Foreign Minister Sergei Lavrov accused Western countries on Sunday of trying to "block" peace negotiations. He also accused Ukrainian authorities of "attempts to disrupt the process that was laid down by presidents Putin and Trump, which has yielded very good results."

Zelenskyy has signaled willingness to meet with Putin, but only after his allies agree on security guarantees for Ukraine to deter future Russian attacks once the fighting stops. 

Norway's government said on Sunday that it will contribute approximately 7 billion Norwegian crowns ($696.12 million) of air defense systems to Ukraine.

Moscow said there could be no discussion about such guarantees, and said any presence of European troops in Ukraine would be "absolutely unacceptable."

Later on Sunday, Russian forces launched a strike on a storage site for Ukrainian missiles and a drone workshop, according to the Russian Defense Ministry.

The strike targeted a storage site for "Sapsan" operational-tactical missiles, a drone production workshop and warehouse, and temporary deployment points for Ukrainian armed formations in 146 areas, the ministry said in a statement.

(With input from agencies)