Russia-Ukraine updates: Russian missiles hit close to nuclear reactors: IAEA director

Ukrainian President Volodymyr Zelenskyy announced a mandatory evacuation of the Donetsk region in eastern Ukraine as fighting intensifies.

"The sooner it is done, the more people leave Donetsk region now, the fewer people the Russian army will have time to kill," Zelenskyy said in a national address on Saturday.

The president additionally urged those in the broader Donbas region "in the areas of the fiercest fighting" to leave.

Governmental officials said they have activated a civil defense law that allows for a mandatory evacuation to be declared. People can still refuse to leave, provided they sign a disclaimer saying they understand all the risks, officials said.

Officials are urging people to leave ahead of winter, as the region's natural gas supplies have been destroyed and there will be no heat.

There are around 200,000 people still in Donbas who need to leave, according to Ukrainian's deputy prime minister, Iryna Vereshchuk.

-ABC News' Patrick Reevell

The number of Russian casualties from the war is "very significant," a senior Pentagon official said Friday.

"And when you look at the numbers of people that they have lost, [it's] impossible to believe that they're not having to figure out ways to replace them if they want to continue to go toe-to-toe with Ukrainians," the official said.

Five months into the war, a senior military official called the invasion "a gigantic strategic failure on the side of the Russians."

"They had to reposition their people out from the north around to the east to try and make some gains. And those gains, as you've seen, have been relatively small -- at a gigantic cost. So I'd really hesitate to give you an idea how long this lasts," the official said. "It certainly looks like it's going to last as [long as] the Ukrainians are able to go toe-to-toe."

-ABC News’ Luis Martinez

Secretary of State Antony Blinken said he spoke with Russian Foreign Minister Sergey Lavrov on Friday. Blinken said he pushed Lavrov to accept the "substantial proposal" the U.S. put forth to free detained Americans Brittney Griner and Paul Whelan.

This marked the first time the two leaders spoke since the war began.

Blinken called it "a frank and direct conversation."

"I pressed the Kremlin to accept the substantial proposal that we put forth on the release of Paul Whelan and Brittney Griner,” he said. "I'm not going to characterize his responses and I can't give you an assessment of whether I think things are more or less likely."

On Russia's stated plans to annex parts of Ukraine, Blinken said he told Lavrov that "those plans will never be accepted. The world will not recognize annexations. We will pose additional significant costs on Russia if it moves forward with its plans."

Blinken did reaffirm that their call did not cover brokering peace in Ukraine.

"Unfortunately, tragically, we've seen no opening--willingness on the part of Russia to engage meaningfully on ending the aggression," Blinken lamented. "At the same time, I've also said that if there are issues where we could make a difference in senior Russians hearing directly from me or from colleagues, we would of course, pursue that."

The Russian Foreign Ministry confirmed the conversation and said it was initiated by the U.S.

The Russian Foreign Ministry said, "Regarding the possible exchange of imprisoned citizens of Russia and the United States, the Russian side is urged to return to the mode of professional, without speculative information stuffing, dialogue in the mode of 'quiet diplomacy.'"

White House spokesperson John Kirby said Friday, "We very much tried to keep details of the negotiations of this nature as private as possible so that we can allow as much space for negotiators to come to a successful conclusion. We felt that in the context of what was happening in both Brittney Griner and Paul Whelan's cases, as well as what was not happening, that it was important to lay out publicly that there was, in fact, a serious offer made by the American side that has not been acted on."

-ABC News’ Shannon Crawford and Molly Nagle

The U.S. doesn’t consider fighting in eastern Ukraine "stalled," White House spokesman John Kirby said Friday.

"I don't believe we consider what's going on in the Donbas is stalled," he said in response to a reporter’s question. “There's a lot of activity still going on in the Donbas."

He did note that over the last "48 to 72 hours, there has not been that many significant changes in the battle lines" in the east and the south.

"It can be true that in some places in eastern and southern Ukraine, the Russians appear to be taking a knee, refitting, refreshing, moving troops around,. And in other places in the east and in the south, there's actual battle going on between Russian and Ukrainian forces," Kirby said.

"There are units that are in actual contact with one another, and there are days where the Russians make a mile or two, and then there are days when the Ukrainians push them back a mile or two. And there's days when the Ukrainians are going on the counter-offensive on a tactical level and then they will stop to reconsider their next move," he said.

-ABC News’ Ben Gittleson