Russian opposition leader Alexey Navalny has been ordered to remain in pre-trial detention for 30 days, following his arrest upon returning to Russia on Sunday for the first time since a failed assassination attempt last year.

Why it matters: The detention of Navalny, an anti-corruption activist and the most prominent domestic critic of Russian President Vladimir Putin, has already set off a chorus of condemnations from leaders in Europe and the U.S.

Russian opposition leader Alexey Navalny was detained upon his return to Moscow on Sunday, which came five months after he was poisoned with the nerve agent Novichok. He returned despite being warned that he would be arrested.

The latest: Navalny was stopped at a customs checkpoint and led away alone by officers. He appeared to hug his wife goodbye, and his spokesman reports that his lawyer was not allowed to accompany him.

Russia will pull out of a longstanding accord that allows countries to conduct fly-over military operations across territories, following in the United States' footsteps after President Trump left the treaty last year, the Russian Foreign Ministry announced Friday.

Why it matters: Russia's exit from the Open Skies Treaty could escalate its rivalry with the U.S. as the country transitions to a new administration under President-elect Joe Biden.

Russian cyber operators are almost certainly still rummaging through U.S. networks, potentially lifting data or setting traps for future havoc even as officials scramble to assess the damage Moscow's hack has already dealt.

Why it matters: The hack, powered by malicious code inserted into an update of SolarWinds network management software, could be among the most significant in the country’s history, perhaps on par with China’s hack of the Office of Personnel Management or Russia’s 2014 hack of the State Department.

A U.S. task force responsible for investigating the massive cyberattack that breached the departments of Defense, State and Homeland Security — among others — identified the hack as "likely Russian in origin," per a joint statement on Tuesday.

Why it matters: This is the first time the federal government has formally named Russia as the likely origin of the attack.

Russian hackers staged their attacks from servers inside the U.S. — sometimes using computers in the same town or city as the victims, cybersecurity company FireEye tells the New York Times.

Why it matters: This let the intruders evade "legal prohibitions on the National Security Agency from engaging in domestic surveillance," and elude "cyberdefenses deployed by the Department of Homeland Security."

Argentina and Belarus on Tuesday became the first countries outside of Russia to begin coronavirus vaccinations using the Sputnik V vaccine, AP reports.

Why it matters: Although both countries authorized the vaccine last week, Russia has yet to complete advanced studies to ensure that Sputnik V is safe, effective and adheres to scientific protocols.

Russia’s prison service has ordered opposition leader Alexei Navalny to return to Moscow by Tuesday morning or face jail if he returns past the deadline, Reuters reports.

The state of play: Navalny, one of Russia's most prominent critics of President Vladimir Putin, has been in Germany since he was airlifted there while recovering from an attempted poisoning attempt.

One of the Russian agents who tailed opposition leader Alexei Navalny before his poisoning with the nerve agent Novichok in August was duped into revealing how the botched operation was carried out in a 49-minute phone call with Navalny himself, CNN and Bellingcat report.

Why it matters: Russian President Vladimir Putin has denied that the Kremlin had any role in Navalny's poisoning, calling the anti-corruption activist a pawn of Western intelligence and claiming that Russian agents "would have probably finished the job" if they were responsible.

The U.S. State Department will close its consulate in Vladivostok, Russia, and suspend operations at the U.S. Consulate General in Yekaterinburg, leaving the embassy in Moscow as the only remaining U.S. diplomatic outpost in Russia, a State Department spokesperson told Axios.

Why it matters: The closures come amid a massive cyberattack on U.S. government departments and agencies — including the State Department — and private companies that Secretary of State Mike Pompeo says was "clearly" carried out by Russia.