In an emotional speech commemorating 31 years of independence, President Volodymyr Zelensky warned Ukrainians that the country was reborn when Russia invaded on February 24 and would reclaim Crimea and seize territory in the east.

In a recorded speech on the six-month anniversary of Russia's invasion on February 24, Mr. Zelensky stated that Ukraine no longer considered the conflict over when there was peace but when Kyiv was victorious.

"A new nation appeared in the world on February 24 at 4 in the morning. It was not born, but reborn. A nation that did not cry, scream or take fright. One that did not flee. Did not give up. And did not forget," he said.

In front of Kyiv's central monument to independence from the Russia-controlled Soviet Union, the 44-year-old wartime leader delivered a speech in his signature fighting fatigues.

"What for us is the end of the war? We used to say peace. Now we say victory," he said.

Following days of grim warnings that Russia could launch further missile assaults against major cities, the streets of central Kyiv were abnormally deserted on Wednesday morning.

Mr. Zelensky said late Tuesday that "repugnant Russian provocations" and "brutal strikes" could cast a shadow on the day.

Officials prohibited public meetings in Kyiv and enforced a strict curfew in Kharkiv, an eastern city that has endured months of shelling. Many government employees were ordered to work remotely.

After the failed putsch in Moscow in August 1991, the overwhelming majority of Ukrainians voted in a referendum to declare independence from the Soviet Union.

Mr. Zelensky said he would honor railroad workers, emergency response personnel, electricians, drivers, artists, and media members to commemorate the occasion.

In defiance, the administration displayed the charred remains of Russian tanks and armored vehicles in the center of Kyiv.

Authorities encouraged individuals to take warnings of air raids seriously and seek shelter when sirens ring.

"We are fighting against the most terrible threat to our statehood and also at a time when we have achieved the greatest level of national unity," Mr. Zelensky said in the Tuesday evening address.

The city government of Kyiv has prohibited big public gatherings until Thursday out of concern that many locals celebrating could become a target for a Russian missile strike.

"They will receive a powerful response," Mr. Zelensky said on Tuesday.

The situation of the Russian-occupied Zaporizhzhia nuclear power station in the southern Ukrainian city of Enerhodar is a significant source of concern for the warring parties and other countries.

Russia and Ukraine have repeatedly accused each other of firing at the plant.

On Tuesday, the UN nuclear watchdog announced that it would visit the plant within days if negotiations to gain access were successful, indicating some movement toward an impartial inspection.

Rafael Grossi, the head of the International Atomic Energy Agency (IAEA), said, "I'm continuing to consult very actively and intensively with all parties."

The plant was seized by pro-Moscow forces shortly after the invasion began, but Ukrainian technicians currently manage it.

The United Nations has called for the demilitarization of the region.