Russian police officers block the street during an unsanctioned anti-war protest rally at Arbat street, on Sept. 21, 2022, in Moscow, Russia.Contributor | Getty Images News | Getty ImagesMore than 1,300 people have been arrested in Russia following President Vladimir Putin’s call-up of extra forces to fight in Ukraine, according to independent human rights group OVD-Info.Around 1,307 people were reportedly detained in 39 cities across the country as of Thursday morning, with the largest numbers arrested in the capital city of Moscow (at least 527) and St. Petersburg (at least 480).Nearly 50 people were arrested in the country’s fourth-largest city of Yekaterinburg, while dozens were also detained in several Siberian cities.Prices of one-way flights out of Russia surged after Putin’s announcement and images on social media appeared to show long queues at border posts.Putin on Wednesday delivered a rare prerecorded televised address to order a partial militarization of reservists to bolster forces in Ukraine, a deeply unpopular move that sparked nationwide protests despite Russia’s harsh laws against criticizing the military and the war in Ukraine.Russia has not yet declared war on Ukraine, despite having invaded in February, and it calls its invasion a “special military operation.”Russian Defense Minister Sergei Shoigu said the mobilization of troops would see 300,000 additional personnel called up to serve in the military campaign in Ukraine.An activist participates in an unsanctioned protest at Arbat Street Sept. 21, 2022 in Moscow, Russia. The sign plays on the word mobilization as “No burialization.”Contributor | Getty Images News | Getty ImagesRussia’s Interior Ministry said servicemen of the Russian Ministry of Internal Affairs took “additional measures” to respond to the anti-war protests and to “ensure public order.””Complications of the operational situation have been prevented,” the ministry said in a statement.”In a number of regions, attempts were made to carry out unauthorized actions, which gathered an extremely small number of participants. All of them were stopped, and the persons who committed offenses were detained and taken to the territorial police units for investigation and prosecution.”‘Reckless’ and ‘irresponsible’In what was widely interpreted as an escalatory address, Putin warned the West he was prepared to use all available means to protect Russian territory. His remarks were seen as a thinly veiled threat that he was prepared to use nuclear weapons.Putin has alluded to Russia’s nuclear weaponry at various points during the conflict with Ukraine. Still, there are doubts over whether Moscow would actually resort to deploying such a weapon, with analysts saying it could be equivalent to starting a third world war.U.S. President Joe Biden condemned Putin’s threat to use nuclear weapons and urged allied U.N. leaders to reject Russia’s invasion of Ukraine.Speaking at the U.N. headquarters in New York City, Biden accused the Kremlin of making “reckless” and “irresponsible” threats and said, “a nuclear war cannot be won and must never be fought.”Ukrainian President Volodymyr Zelenskyy reportedly said on Wednesday in an interview with Germany’s Bild online television channel that he didn’t believe the world would allow Putin to use nuclear weapons.— CNBC’s Holly Ellyatt contributed to this report.