Russians took to the streets, and to the skies, on Wednesday in opposition to Vladimir Putin's mobilization order that sent reservists to fight in Ukraine as his threats of nuclear war intensified.

The order, which would send 300,000 more soldiers into the increasingly desperate fight, sparked a wave of protests across Russia and a run for one-way tickets out of the country.

The mobilization was accompanied by chilling threats to defend Russian territory with nuclear weapons, as the Kremlin planned to call a quarter of Ukraine part of Russia.

"I want to remind you that our country also has various means of destruction," Putin said in a televised address Wednesday morning. "When the territorial integrity of our country is threatened, in order to protect Russia and our people, we will certainly use all means at our disposal."

With an icy look at the camera, the Russian strongman added: "It's not a hoax."

Putin's threat to use nuclear weapons to defend Russia's "territorial integrity" comes as his puppet regimes in Ukraine prepare to declare occupied parts of that country Russian territory.

This week four referendums are planned for Ukraine's occupied provinces (Luhansk, Donetsk, Zaporizhzhia and Kherson) to declare those provinces part of Russia.

Such a vote would make the territories an "irreversible" addition to the country, allowing Moscow to use "any means" to defend them, Dmitry Medvedev, head of the Kremlin Security Council, said this week.

"The invasion of Russian territory is a crime that allows you to use all the forces of self-defense," Medvedev added on the Telegram messaging application.

The vote, scheduled to start on Friday, has already been declared illegitimate by Ukraine and its Western allies.

Russia's use of so-called filter camps to relocate Ukrainians within the occupied territories, and its alleged use of torture, captivity and extrajudicial executions against those it suspects of supporting or aiding Kyiv, undermines the notion that any referendum held in occupied territory could reflect the will of the neighbors.

President Biden responded to Putin's comments on Wednesday as he addressed the United Nations General Assembly in New York.

"This war is about extinguishing Ukraine's right to exist as a state, plain and simple, and Ukraine's right to exist as a people," Biden said. “Whoever you are, wherever you live, whatever you believe, that…should make your blood run cold.”

He criticized the Russian leader for "making irresponsible nuclear threats," adding that "a nuclear war cannot be won and should never be fought."

Putin's announcements caused panic in Russia, with a wave of protests across the country.