Russia's military has announced another temporary cease-fire in Ukraine beginning Tuesday at 10 a.m. local time and said it is prepared to open humanitarian corridors from Kyiv and several other key Ukrainian cities it has encircled.

In a statement, the Russian Ministry of Defense said the corridors would allow people to go north to Russia and its ally Belarus, adding that it would also allow routes in some places to other parts of Ukraine.

The ministry said there will be corridors from Kyiv, as well as the northern cities Chernihiv and Sumy and the key eastern cities Kharkiv and Mariupol.

Russia had initially proposed corridors only to Russia and Belarus, which Ukraine had rejected as "immoral."

However, Russia has previously violated its own cease-fire, shelling evacuation areas, and it is unclear if corridors for people to move within Ukraine will actually be made available.

Russian President Vladimir Putin also said in a video address that Russia will not call up additional reservists or send in conscripts to fight the war in Ukraine, saying it will be fought only by professional soldiers.

"The tasks are solved only by professional military personnel," Putin said. "I am sure they will reliably ensure security and peace for the people of Russia."

His comments came in a video message to Russia's women on International Women's Day, saying he understood the concerns of the "mothers, wives, sisters, brides and girlfriends of our soldiers and officers who are now in battle, defending Russia during a special military operation."

Some reports indicate that Russian conscripts have been pressured into signing professional contracts before being deployed into Ukraine.

-ABC News' Patrick Reevell

The U.N. Security Council met again this afternoon to discuss Russia’s war against Ukraine and the growing humanitarian crisis.

U.N. relief chief Martin Griffiths briefed the council, warning that U.N. agencies are being overwhelmed.

“Make no mistake. We are unable to meet the needs of civilians today,” Griffiths said. “We’re failing to meet the needs of civilians today at this time. I hope we will not fail them tomorrow.”

President Joe Biden’s envoy to the U.N. Linda Thomas-Greenfield said in the meeting that 100 Ukrainian refugees cross into Poland every minute.

Griffiths urged both sides to take “constant care to spare civilians and civilian homes and infrastructure,” including safe passage for civilians to leave war zones and allow aid to come in. He also said the U.N. was working with Russia to set up a humanitarian notification system to ensure aid can be delivered safely and at scale.

“Simply put, millions of lives shattered. People can’t stay home with shops shut, power and water cut, shells falling, phones switched off. They can’t find what they need, even if they have money to pay for it. And as we have seen, even as the TV cameras roll, many can’t flee in safety either in this conflict,” he said. “It’s been 11 days of escalating violence, fear, and pain.”

-ABC News’ Conor Finnegan

After Ukrainian President Volodymyr Zelenskyy told ABC News’ David Muir that he believes President Joe Biden can do more to facilitate getting Polish fighter jets to Ukraine, the Biden administration said it is ultimately up to Poland.

“This is Poland’s sovereign decision to make,” White House press secretary Jen Psaki told ABC News’ Cecilia Vega. “We have in no way opposed Poland transferring planes to Ukraine.”

Psaki said there are “practical questions” to consider, such as how the planes would be transferred and where they would depart from and land. She also noted that procuring new planes and transferring serious weapons systems often takes years -- so a speedy transfer would represent a major challenge.

Vega asked Psaki if it was just logistical issues or whether Biden was concerned that supplying planes to Poland would “exacerbate the conflict.”

The press secretary said there are logistical challenges and that they’re “looking at all of those factors.”

“But we are not certainly preventing or blocking or discouraging Poland,” Psaki said. “That is, they are a sovereign country. They make their own decisions, but it is not as easy as moving planes around.”

-ABC News’ Sarah Kolinovsky

New York City has gone from a "high alert" to an "ultra-high alert" for potential cybersecurity attacks on critical city infrastructure following the Russian cyber-aggression in Ukraine, a New York Police Department official said Monday.

NYPD Deputy Commissioner John Miller said during a news conference that normally the city is on "high alert" for cyberattacks, but a difference between "high" and "ultra-high" alerts is that they can attribute possible cyber threats to "state actors." When tensions rise between the United States and Russia, so does the threat for tactical and strategic cyberattacks, Miller said.

"There is no guarantee that those attacks will be limited to Ukraine," Gillibrand said. "The decision to impose sanctions on Russia puts the country at an increased risk that Russia will carry out retaliatory cyberattacks, particularly against New York state infrastructure and individuals."

When asked during the news conference if there have been any potential direct Russian cyberattacks against New York, New York City Chief Technology Officer Matthew Fraser said, “we have seen an uptick [in cyber threats], but we are not aware of any campaign that's explicitly targeting the city itself."

-ABC News' Victoria Arancio

U.S. Secretary of State Antony Blinken crossed the border into Ukraine Saturday after meeting with Ukrainian Foreign Minister Dmytro Kuleba at the Korczowa Border Crossing Point.

"The entire world stand with Ukraine," Blinken said, and Kuleba added that he hopes Ukrainians will see this as a "clear manifestation that we have friends who literally stand by us."

Blinken said the sanctions imposed so far against Russia are "producing very, very concrete results" and that the pressure will "grow" until this "war of choice is brought to an end."

When asked directly about helping Kuleba with more firepower, Blinken said, "the support for Ukraine not only has been unprecedented, not only is going to continue, it's going to increase."

Kuleba said Ukraine "appreciates" sanctions that have been announced in the last week, but that more economic and political pressure and "necessary weapons," would "save many lives in Ukraine... many sufferings will be avoided."

Kuleba also said that they are “satisfied" with already arranged supplies of anti-tank weapons and ammunition, but that “it’s no secret” they still want fighter jets and air defense systems.

He also thanked the U.S. for sending stingers, and said they were used on Saturday.

"Just today we shot down three Russian attack aircrafts, which were bombing our cities with the use of stingers but we need -- so to say -- big air defense systems to ensure the safety of our skies. If we lose the skies, there will be much, much more blood on the ground,"Kuleba said.

In response to questions about NATO’s refusal to impose a no-fly zone over Ukraine, Kuleba said it’s a "sign of weakness," but stayed optimistic that they will change their minds.

"The time will come," he said.

-ABC News' Conor Finnegan and Justin Gomez