Finland will formally join NATO in the "coming days," after the country was able to clear its final hurdle, according to NATO Secretary General Jens Stoltenberg.

"Their membership will make Finland safer and NATO stronger. Finland has highly capable forces, advanced capabilities and strong democratic institutions. So Finland will bring a lot to our alliance," Stoltenberg said in a statement Friday.

Turkey was the last of the 30 NATO allies to approve Finland's bid to join the alliance.

-ABC News' Will Gretsky

Russia just struck Kharkiv in eastern Ukraine with multiple missiles, Ukrainian officials said Thursday night.

Local officials in Kharkiv said Russia fired six Soviet-era S-300 surface-to-air missiles.

ABC News reporters heard explosions outside the city center and saw Ukrainian air defense active just before and during the attacks.

There are currently no reports of casualties or damage to infrastructure as a result of the strikes in Ukraine's second-largest city.

There are also reports of Russian strikes in the Dnipro region.

-ABC News' Tom Soufi Burridge

Russian President Vladimir Putin signed a decree on Thursday ordering a spring conscription. Russia will call up 147,000 people to join the Russian Armed Forces from April 1 to April 15.

-ABC News' Will Gretsky

Russian media reporting suggests authorities are preparing to start a major military recruitment aiming to sign up an additional 400,000 troops, the United Kingdom's Defense Ministry assessed.

Russia is presenting the campaign as a drive for volunteer, professional personnel, rather than a new, mandatory mobilization. There is a realistic possibility that in practice this distinction will be blurred, and that regional authorities will try to meet their allocated recruitment targets by coercing men to join up, UK officials said.

Russian authorities have likely selected a supposedly ‘volunteer model’ to meet their personnel shortfall in order to minimize domestic dissent. It is highly unlikely that the campaign will attract 400,000 genuine volunteers, according to UK officials.

However, rebuilding Russia’s combat power in Ukraine will require more than just personnel; Russia needs more munitions and military equipment supplies than it currently has available, UK officials said.

The Russian oligarch behind the Wagner private paramilitary group fighting for the Kremlin in Ukraine is threatening a mutiny if his forces are not resupplied with ammunition soon.

Yevgeny Prigozhin, owner and curator of the Wagner group, penned a letter to Russian Defense Minister Sergei Shoigue, demanding ammunition be provided to his forces on the battlefield.

In the letter, Prigozhin wrote that if supply problems are not fixed fast, he will complain to Russian President Vladimir Putin and his mercenaries would abandon their positions in Bakhmut, Ukraine, where heavy fighting has been going on for weeks, The Moscow Times reported.

“I appeal to Shoigu with a request to immediately issue ammunition. In case of refusal, I consider it necessary to convey to the Supreme Commander-in-Chief information about the existing problem in order to make a decision and about the advisability of further presence of Wagner PMC in Bakhmut in the conditions of a shortage of ammunition," Prigozhin wrote.

He added, "If the deficit is not replenished ... we will be forced to withdraw part of the units from this territory, and then everything else will crumble. Therefore, the bell is already ringing -- it is called an alarm."

Emphasizing the urgency, Prigozhin noted that Ukraine is planning to launch a counteroffensive soon.

There was no immediate public response from Shoigu or the Kremlin.

"We need to stop deceiving the population and telling that everything is fine with us," Prigozhin wrote. "I must honestly say: Russia is on the brink of disaster. If these screws are not adjusted today, the 'aircraft' will crumble in the air."