Russia has restricted civilian flights over the Black Sea and the Crimean Peninsula, amid rising tensions with Ukraine and its Western supporters.”The area has been declared temporarily dangerous for aircraft flights,” Interfax news agency reported on Tuesday, citing an alert to pilots.Kremlin spokesman Dmitry Peskov called the flight restrictions an “absolutely normal world practice” in a press briefing on the same day.But the alert raised the specter of war in a region fraught with military tensions. Russia’s Defense Ministry previously said it had closed off navigation in parts of the Black Sea to foreign military and commercial ships from mid-April until the end of October for naval and aviation drills.The flight restrictions come amid an escalation of tensions between Russia and the United States and NATO over Ukraine.Russia has built up troop presence near the Ukrainian border amid increased activity by NATO forces in the region. The US and other NATO members have deployed military forces to the region as well.Ukraine’s Foreign Minister Kubela Dmytro has claimed that 120,000 Russian troops have been deployed to the country’s border within a week.Dmytro said a regiment of Russian paratroopers had also been stationed in Crimea in what appeared to be a permanent deployment.Russia says the troop build-up is a response to heightened NATO activity near its borders in Ukraine. Moscow has warned that the US and NATO are turning Ukraine into a “powder keg” by increasing arms supplies to Kiev and inflaming tensions in the country’s volatile east, where government forces are fighting ethnic Russians.Separately, Ukrainian President Volodymyr Zelensky has acknowledged that Kiev and Moscow hold different views about the conflict in the Russian-speaking east of Ukraine.Zelensky insisted on Tuesday that the difference of opinion about the future of the Ukrainian region was to be seen as an opportunity rather than a problem.He invited Russian President Vladimir Putin to meet for peace talks “at any location” in the war-torn Ukrainian region of the Donbass.In a video address released on Tuesday, Zelensky said that advisers to the leaders of the Normandy Quartet (Germany, Russia, Ukraine, and France), as well as the Contact Group on Ukrainian reconciliation had discussed restoring a full ceasefire in the Donbass on Monday and Tuesday.”I am ready to… invite you to meet in any part of the Ukrainian Donbass, where war is ongoing,” Zelensky said, directly addressing Putin.The Ukrainian president, elected in 2019 on promises to bring an end to the eastern Ukraine conflict, accused Russia of participating in peace negotiations while massing troops on Ukraine’s border.”A considerable number of Russian troops are concentrated near our border,” he said. “Officially, Russia calls this military exercises. Unofficially, the whole world calls this blackmail.””The Russian president once said that if a fight is inevitable, you need to hit first. But every leader needs to understand that a fight must not be inevitable when it… concerns a real war and millions of human lives,” Zelensky said.He said that although Ukraine did not want war, it was prepared to fight.”Will Ukraine defend itself if something happens? Always. Our principle is simple: Ukraine does not start a war first, but Ukraine always stands to the last,” the comedian-turned-politician said.The United States has committed over two billion dollars in military assistance to Kiev since 2014.In March, the US Department of Defense announced an additional 125-million-dollar package for the Ukrainian military to cover training, equipment, and advisory support.The armed confrontations in eastern Ukraine began when a wave of protests in Ukraine overthrew a democratically-elected pro-Russia government and replaced it with a pro-West administration.The new government began a crackdown on the mainly ethnic Russians in the east, who in turn took up arms and turned the two regions of Donetsk and Lugansk — collectively known as the Donbass — into self-proclaimed republics.Kiev and its Western allies accuse Moscow of having a hand in the crisis. Moscow, however, denies the allegations.Relations between Moscow and Kiev further deteriorated when the Black Sea peninsula of Crimea voted in a referendum in 2014 to fall under Russian sovereignty.In 2015, the warring sides signed a ceasefire deal in the Belarussian capital, Minsk, with French and German support, but both parties have on numerous occasions accused each other of violating the ceasefire.Russia has accused Ukraine of failing to implement agreements over the region.In related news, France said on Tuesday that a new attack on Ukraine’s sovereignty by Russia would be “unacceptable” and would not be “without consequences.”Separately, the Kremlin suggested that US Ambassador to Moscow John Sullivan return home for consultations amid a diplomatic crisis between Moscow and Washington, the Interfax news agency reported.Russian Foreign Minister Sergei Lavrov put forth the suggestion to Sullivan during a news conference, in which he also said Moscow would ask 10 US diplomats to leave the country in retaliation for Washington’s expulsion of the same number of Russian diplomats over alleged malign activity.Russia has already recalled its ambassador to Washington for consultations following a remark by US President Joe Biden calling President Putin a “killer.”Ukraine, NATO continuing military preparations: Russia RIA news agency cited Russia’s Foreign Ministry as reporting that Ukraine and NATO were continuing military preparations in the region. It said Russia had warned Ukraine on Wednesday against actions that would lead to the further escalation of tensions in the region. Meanwhile, Zelensky signed a law allowing reservists to be called up for military service without announcing mobilization, his office said on Wednesday.