Russia has been holding last-minute military exercises near commercial shipping lanes in the Black Sea that threaten to strangle Ukraine's economy, according to an internal document from Ukraine's ministry of defense reviewed by Axios.

Why it matters: With the eyes of the world on the massive buildup of troops in eastern Ukraine, the leaked memo shows Russian forces escalating their presence on all sides of the Ukrainian border.

Russian opposition leader Alexei Navalny has been transferred to a hospital in another penal colony, one day after his doctor warned that the jailed Putin critic "could die at any moment," Russia's prison service said Monday.

Why it matters: News that Navalny's condition had severely deteriorated on the third week of a hunger strike prompted outrage from his supporters and international demands for Russia to provide him with immediate medical treatment.

The Biden administration warned the Russian government "that there will be consequences" if jailed Russian opposition leader Alexei Navalny dies, National Security Adviser Jake Sullivan told CNN on Sunday.

The big picture: Sullivan also defended President Biden for not mentioning Navalny in a Thursday speech about Russia or in a Tuesday call with Russian President Vladimir Putin, saying the White House aims to deal with the issue "privately and through diplomatic channels."

Jailed Russian opposition leader Alexei Navalny faces possible kidney failure as he continues his multi-week hunger strike, a medical trade union told Reuters on Saturday.

What they're saying: "His condition is indeed critical ... His potassium is high and he has other high readings which indicate that his kidneys may soon fail. This would lead to severe pathology and cardiac arrest may occur," Alexandra Zakharova, a representative for the Doctors Alliance trade union, told Reuters.

Russia on Saturday said it would expel a Ukrainian diplomat it accused of trying to obtain classified information, prompting Ukraine to say it would do the same to a Russian diplomat, according to Reuters.

Why it matters: The tit-for-tat expulsions come amid heightened tensions between the two countries over Russia's build-up of military personnel and equipment on Ukraine's eastern border where Ukrainian soldiers are fighting Kremlin-back separatist troops.

Russia will expel 10 U.S. diplomats and add eight current and former U.S. officials to its no-entry list in retaliation for sanctions that the Biden administration leveled at Moscow on Friday, Russian foreign minister Sergey Lavrov said Friday.

Why it matters: The measures come after the U.S. said it would expel 10 Russian intelligence officers operating under diplomatic cover, as part of a broad package of sanctions retaliating against the SolarWinds hack of federal agencies and Russia's interference in the 2020 election.

Despite bold talk from top administration officials, there's little reason to think the Russia sanctions package President Biden announced Thursday will do anything to alter Russian President Vladimir Putin's behavior or calculus.

Why it matters: While it's true some elements of the package — namely, the targeting of Russia's sovereign debt — represent significant punitive measures against Moscow, it leaves plenty of wiggle room for the Russian president.

U.S. intelligence officials have "low to moderate confidence" in reports that surfaced last year that Russia had offered bounties to Taliban-linked militants for killing U.S. troops stationed in Afghanistan, according to The Guardian.

Why it matters: The news comes as the Biden administration unveiled a spate of sanctions against Russian officials and entities on Thursday. The bounty reports, however, were not a factor in the decision to pass sanctions.

The Biden administration announced it will sanction dozens of Russian officials and entities, expel 10 diplomats from the U.S., and set new restrictions on buying Russian sovereign debt in response to the massive SolarWinds hack of federal agencies and interference in the 2020 election.

Why it matters: The sweeping acts of retaliation are aimed at imposing heavy economic costs on Russia, after years of sanctions that have failed to deter an increasingly aggressive and authoritarian President Vladimir Putin.

The U.S. government has sanctioned Konstantin Kilimnik, a Russian-Ukrainian political consultant indicted in the Mueller investigation in 2018, for carrying out election influence operations on behalf of Russian intelligence services.

The big picture: The Senate Intelligence Committee's report on 2016 Russian election interference assessed that Kilimnik, who worked with former Trump campaign manager Paul Manafort as a lobbyist for the pro-Russia president of Ukraine, is a Russian intelligence officer.