The U.S. State Department on Saturday updated its travel advisory for Russia amid the war in Ukraine and Russia's tightening crackdown on dissent, reporting and travel and the worsening economic situation, including declined credit cards and cash shortages.

"U.S. citizens should depart immediately," the advisory warns, adding, "If you wish to depart Russia, you should make arrangements on your own as soon as possible."

The State Department warned Americans, "If you plan to stay in Russia, understand the U.S. Embassy has severe limitations on its ability to assist U.S. citizens, and conditions, including transportation options, may change suddenly."

The State Department further warned U.S. citizens may be harassed by "Russian government security officials" or face "arbitrary enforcement of local law," something they've warned about for years.

The U.S. embassy has issued detailed instructions on how to flee the country, including over land borders by car and bus as well as limited flights.

-ABC News' Conor Finnegan

Russia’s Defense Ministry on Saturday announced it will now begin offensive actions again in Ukraine, having never observed the cease-fire it announced earlier in the morning.

A Defense Ministry spokesman, in a briefing, accused Ukraine’s government of failing to restrain “nationalists” or observe the cease-fire saying, “at 18:00 Moscow-time offensive actions are renewed.”

In reality, Russia has continued to shell Mariupol and Volnovakha in Ukraine’s east throughout the day, despite having declared a temporary cease-fire and humanitarian corridor to allow civilians to leave.

Ukrainian officials have accused Russia of using the cease-fire period to move forces closer to Ukrainian positions.

The International Committee of the Red Cross has said evacuations could not take place today because of shelling. The ICRC branch in Donetsk told ABC News earlier, that its team in Mariupol was forced to take shelter because of shelling.

-ABC News' Patrick Reevell

Ukrainian President Volodymr Zelenskyy spoke to over 300 senators, members of Congress and top Hill staff on Saturday, pleading for more lethal and military aid.

Zelenskyy, on an hourlong Zoom call, asked U.S. lawmakers for weapons including drones, planes and stingers; the implementation of a "no-fly" zone over Ukraine; a full ban on the import of Russian oil to the U.S.; and a suspension of the use of Visa and MasterCard in Russia.

In a statement made after the call, Senate Majority Leader Chuck Schumer said, “President Zelenskyy made a desperate plea for Eastern European countries to provide Russian-made planes to Ukraine. These planes are very much needed. And I will do all I can to help the administration to facilitate their transfer.”

According to a source who attended the meeting, Schumer started the call by addressing Zelenskyy, saying, “Mr. President, we are inspired by you and the strength and courage of the Ukrainian people. The people of New York and its large Ukrainian community stand with you."

“Senator McConnell and I, along with the other members on this zoom, are working very hard in a bipartisan fashion to get all the assistance the administration has requested for the Ukrainian people. Together we will get that assistance of over $10 billion in economic, humanitarian and security assistance to the Ukrainian people quickly," Schumer said.

One senator on the call told ABC News' Rachel Scott that at one point, dozens of attendees unmuted and said "Thank you, Mr President," "We support you," "Slava Ukraini" and "We will help you."

The senator told Scott that Zelenskyy "was clearly moved by the cascade of voices lifted in support."

Senators Rob Portman and Jeanne Shaheen, who recently traveled to Ukraine, are expected to send a letter asking the Department of Defense to send F16 planes to Eastern European countries who donate MiG aircrafts to Ukraine. Poland has said it is willing to do this.

Another senator told ABC News that there are serious concerns about Zelenskyy's safety, saying, "If he’s dead it makes it that much easier for Russians to seize control. If there isn’t a legitimate government we recognize it’s harder to help."

According to a source, Zelensky said he and his family have been targeted.

The U.S. Department of the Treasury said Friday that sanctions don't start until June and omit Russian oil and gas. Senators are going to call for immediate tightening.

-ABC News' Trish Turner, Rachel Scott, Mariam Khan and Ben Siegel

The U.S. on Saturday confirmed that it approved a flight chartered by the Russian government to pick up the Russian United Nations Mission personnel who were ordered expelled earlier this week for reportedly spying, State Department spokesperson confirmed to ABC News.

"This special exception was done in accordance with federal regulations to ensure Russian mission personnel and their families departed by the date we had instructed," the spokesperson said.

-ABC News' Conor Finnegan

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