Twelve Russian diplomats have been expelled from Moscow’s mission to the United Nations in New York, U.S. Ambassador Richard Mills, the deputy representative to the U.N., confirmed on Monday.

Those diplomats were engaged in activities not in accordance with their obligations and responsibilities as diplomats, Mills said.

They "abused their privileges of residency in the U.S. by engaging in espionage activities that are adverse to our national security," Olivia Dalton, spokeswoman for U.S. Ambassador Linda Thomas-Greenfield, tweeted Monday. The action to expel them “has been in the works for several months,” Dalton wrote.

Russian Permanent Representative to the U.N. Vasily Nebenzya in a Monday press conference in New York accused U.S. authorities of undertaking "another hostile action against the Russian Federation's mission to the United Nations" and of "grossly violating their commitments on the host country agreement that they undertook" with this move.

The expelled employees are now considered "personae non gratae" and were ordered to leave the U.S. by March 7, according to Nebenzya.

-ABC News’ Conor Finnegan and Tanya Stukalova

The U.S. is supporting an international effort to "detect and document potential human rights violations" for abuses of international humanitarian law, potential war crimes and "other potential atrocities" committed by Russia, Department of State Spokesman Ned Price announced Monday.

The U.S. will use "every tool available, including criminal prosecutions where appropriate," Price said in a warning to "the government of Russia and all Russian personnel involved in these operations" against Ukraine.

Price said the U.S. is concerned by reports of civilians killed, schools and kindergartens destroyed, and other civilian targets impacted.

Hours before the physical invasion into Ukraine, Microsoft detected a new round of "offensive and destructive" cyberattacks directed at the Ukrainian government, a top Microsoft official announced.

"In recent days, we have provided threat intelligence and defensive suggestions to Ukrainian officials regarding attacks on a range of targets, including Ukrainian military institutions and manufacturers and several other Ukrainian government agencies," President and Vice Chair of Microsoft Brad Smith wrote in a blog post Monday. "This work is ongoing."

Microsoft remains concerned about the cyber threat emanating from Ukraine, "especially" recent cyberattacks on Ukrainian civilian digital targets, including on the financial sector, agriculture sector, emergency response services, humanitarian aid efforts and energy sector organizations, Smith said.

"These attacks on civilian targets raise serious concerns under the Geneva Convention, and we have shared information with the Ukrainian government about each of them," he wrote.

Microsoft has advised the Ukrainian government about recent cyber efforts to steal a wide range of data, including health, insurance and transportation-related personally identifiable information, as well as other government data sets, Smith said. Microsoft is also sharing information with U.S. officials.

Over the weekend, the U.S. warned that a cyberattack in Ukraine could have ripple effects in the U.S.

"Further disruptive cyberattacks against organizations in Ukraine are likely to occur and may unintentionally spill over to organizations in other countries," the FBI, DHS and CISA warned in a statement, saying Russia has taken these steps in the past. "Organizations should increase vigilance and evaluate their capabilities encompassing planning, preparation, detection, and response for such an event."

Microsoft is "swiftly" removing Russian propaganda from their websites from the Windows app store, including RT, the Russian state-controlled international television network.

"We are also focused as a company in protecting against state-sponsored disinformation campaigns, which have long been commonplace in times of war," Smith wrote.

This comes as Meta, the parent company of Facebook, announced efforts it was taking to disrupt social media misinformation campaigns.

-ABC News’ Luke Barr and Cindy Smith

In an extraordinary emergency meeting of the U.N. General Assembly -- only the 11th in the body’s history -- representatives from Ukraine and Russia delivered fiery back-to-back remarks.

Ukrainian Ambassador to the U.N. Sergiy Kyslytsya compared Russian President Vladimir Putin to Adolf Hilter.

“This war was not provoked. It was chosen by someone who is right now sitting in the bunker. We know what happened with the person who sat in the bunker in Berlin in May 1945," he said.

Kyslytsya accused Russia of carrying out war crimes, saying Russians "keep attacking kindergartens and orphanages, thus committing war crimes and violating the Rome Statute. Hospitals and mobile medical aid brigades are also targeted by the Russian shelling and sabotage groups working in Ukraine cities and towns.”

He concluded with an appeal for support, stressing that it was not just Ukraine at stake.

“If Ukraine does not survive, international peace will not survive," he said.

Russian Ambassador Vasily Nebenzya denied the veracity of many of Kyslytsya’s claims, saying instead of discussing the roots of the “disinformation,” he wished to focus on the “real reasons for the crisis,” saying the fault lies with Ukraine itself. He cited baseless Kremlin-peddled claims that the country was carrying out a brutal attack on the people of the Donbas region and accused Western powers of turning “a blind eye."

Nebenzya also attempted to shift blame to the West.

“Our Western colleagues have shamelessly inundated the country with weapons, have sent to the country instructors, and effectively incited Ukrainians who are facing a 120,000-strong military contingent, and prompted them to engage in armed provocation again the Donbas,” he said.

This phase of debate on a resolution condemning Russia’s actions in Ukraine has now concluded and the General Assembly is expected to vote on the resolution later on Monday.

-ABC News' Shannon Crawford

Secretary of State Antony Blinken closed his remarks to the U.N. Security Council meeting by challenging the Russian Federation to "announce today -- with no qualification of equivocation or deflection -- that Russia will not invade Ukraine, stated clearly stated plainly, to the world."

"And then demonstrate it by sending your troops, your tanks, your planes back to their various can hangars and sending your diplomats to the negotiating table," he added.

Blinken laid out how the U.S. believes Russia will attack Ukraine -- but said he would welcome being wrong and for Russia to withdraw.

"Now, I'm mindful that some have called into question our information, recalling previous instances where intelligence ultimately did not bear out," he said, apparently referring to a similar address then-Secretary of State Colin Powell famously made to the Security Council presenting U.S. intelligence to justify the Iraq War. "But let me be clear, I am here today not to start a war, but to prevent one," he said, citing allies that agree with U.S. assessments.

"If Russia doesn't invade Ukraine, then we will be relieved that Russia changed course and proved our predictions wrong. That would be a far better outcome in the course we're currently on. And we'll gladly accept any criticism that anyone directs at us," Blinken said.

He continued, "Russia can still make if there's any truth to his claim that is committed to diplomacy. Diplomacy is the only responsible way to resolve this crisis"

Blinken also said that he sent a letter to Russia's Foreign Minister Sergei Lavrov earlier Thursday proposing that they meet next week in Europe following their talks in recent weeks "to discuss the steps that we can take to resolve this crisis without conflict" and that U.S. is also proposing meetings at the NATO Russia Council and the OSC Permanent Council.

"These meetings can pave the way for a summit with key leaders in the context of de-escalation to reach understandings on our mutual security concerns," he added.