Pope Francis renewed calls on Sunday for a cease-fire in Ukraine to allow humanitarian aid to reach the war-torn country's "exhausted population."

The pope told tens of thousands of people gathered in St. Peter's Square at the Vatican that Sunday marked both Orthodox Easter and two months since the Russian invasion of Ukraine began.

"Instead of stopping, the war has become harsher," Francis said.

He urged political leaders on both sides of the conflict "to listen to the voice of the people, who do not want an escalation of the conflict."

"I renew an appeal for an Easter truce, the minimum and tangible sign of a willingness for peace. Stop the attacks in order to help the exhausted population. Stop," Francis said.

Even as the pope spoke, Ukrainian officials reported shelling in Ukraine on Sunday as Russian forces pushed forward with a new offensive targeting eastern Ukraine's Donbas region and territory in southern Ukraine. Two children were among those killed in shelling on Sunday, according to Ukrainian officials.

"It is sad that in these days that are the holiest and most solemn for all Christians, the deadly sound of weapons is heard more than the sound of bells that announce the resurrection," Francis said. "And it is sad that weapons are increasingly taking the place of words."

The 85-year-old pontiff did not specifically mention Russia or President Vladimir Putin, but left little doubt which side he was most critical of, using terms such as "unjustified aggression" and lamenting atrocities against civilians.

Putin, a member of the Russian Orthodox Church, has described Moscow's actions as a "special military operation" in Ukraine aimed at demilitarizing and "denazifying" the country. Moscow has denied targeting civilians.

"I ask everyone to pray more for peace and to have the courage to say and demonstrate that peace is possible," the pope said.

-ABC News' Rashid Haddou

Ukrainian President Volodymyr Zelenskyy released an Orthodox Easter message Sunday, saying he believes in a "new victory for Ukraine."

In a video of his Easter greetings posted on YouTube, Zelenskyy said he was was speaking from the Cathedral of St. Sophia in Kyiv and cited the church's thousand-year history in which it survived the Kyivan Rus’-Ukraine war against the Pechenegs and withstood Nazi occupation.

"Today, we all believe in a new victory for Ukraine," Zelenskyy said. "And we are all convinced that we will not be destroyed by any horde or evil."

Zelenskyy added, "We are enduring dark times. And on this bright day, most of us are not in bright clothes. But we are fighting for a bright idea."

Reciting a prayer, Zelenskyy asked God to protect Ukrainians and give the nation "strength to fight and win."

"This Easter, we ask God for great grace to make our great dream come true -- a dream of another great day, a day when great peace will come to Ukraine and with it eternal grace and prosperity," Zelenskyy said. "With faith and confidence in this, I wish you all a Happy Easter."

Gathering outside bombed churches, Ukrainians marked Orthodox Easter on Sunday in the capital of Kyiv and throughout the country with prayers for peace and the safety of soldiers fighting on the front lines.

Among those attending an Easter service at at Pyrohoshcha Dormition of the Mother of God Church in Kyiv was Inna Tsarkova, who told ABC News she was praying for the safety of her son, Roman, who she hasn't heard from in 11 days.

"(Easter) is much different because of the war. It’s supposed to be a very cheerful day. But right now we don’t know what the future is for Ukraine," Tsarkova said. "I hope he’s OK, that he will come back. There is no joy for Easter this year. Eleven days is a lot, it’s a lot for me to not talk with my son."

Elsewhere in Ukraine, worshipers gathered for an Easter service outside The Nativity of the Holy Virgin Church in the Kyiv suburb of Peremoha because the church was heavily damaged by Russian shelling. During the service, an Orthodox priest sprinkled holy water on believers lined up outside the church.

In Krakow, Poland, Ukrainian refugees lined the street outside the Orthodox Church of the Assumption for a Easter Mass.

About 200,000 displaced Ukrainians have sought refuge in Krakow, where the local Orthodox church has been struggling to provide shelter and humanitarian aid to the refugees.

Large TV screens were installed outside the Church of the Assumption so devotees who couldn't fit inside could participate in the service. Following the service, the church held a procession and blessing of food baskets that were given away to those in attendance.

Ukrainian Deputy Prime Minister Iryna Vereshchuk told ABC News that an anticipated visit to Ukraine on Sunday by U.S. Secretary of State Antony Blinken and Defense Secretary Lloyd Austin will focus on logistics of funneling more military assistance to the country's embattled troops to fight off Russian forces.

Vereshchuk told ABC News' foreign correspondent James Longman that the face-to-face visit will also give Ukrainian leaders a better chance to express the urgency and turmoil of their predicament.

"When you talk on the phone, the emotional part of the conversation cannot be conveyed," Vereshchuk said.

Vereshchuk said it is incumbent on NATO to step in, given Russia's apparent plans to take the Donbas region in eastern as well as territory in southern Ukraine.

She expressed disappointment in Germany for seemingly dragging its feet on sending heavy artillery, including tanks, to Ukraine and said it appeared German leaders are attempting to placate Putin.

“They don’t understand. There is no way to pacify Putin," Vereshchuk said. "It would be a huge problem for NATO if Russia has dominance over the Black Sea.”

German Chancellor Olaf Scholz has defended the support his country has sent Ukraine, saying last week, “The weapons we are delivering have made a very substantial contribution" to Ukraine fight against Russia."

"We are delivering, we have delivered and we will deliver," Scholz said.

Vereshchuk also told ABC News that about 200 Russian soldiers have been exchanged for Ukrainian soldiers, so far. She said the highest ranking Russian military leader captured by Ukraine was a lieutenant colonel.

Vereshchuk, who is in charge of prisoner exchanges for her country, said Ukraine won’t exchange those responsible for war crimes.

Vereshchuk also claimed that 200,000 Ukrainians have been forcibly deported to Russian-controlled territory into "filtration camps," including 5,000 children.

"We saw what Stalin did, we know what they are," Vereshchuk said of the camps.

Jalina Porter, the State Department's deputy spokesperson, is responding to the Russian attack at a Ukraine train station that killed at least 50, saying, "We can no longer be surprised by the Kremlin's repugnant disregard for human life."

Five children were among those killed when Russian rockets struck the station in Kramatorsk in Donetsk Oblast on Friday morning, according to Ukraine's state-owned railway company. At least 100 people were injured, according to Donetsk Oblast Gov. Pavlo Kyrylenko.

Russia has denied involvement in the attack, which occurred as "thousands" of civilians fleeing the Russian invasion were at the train station waiting to be taken to "safer regions of Ukraine," according to Kyrylenko.

"Civilians are killed when they stay in their homes, and they're killed when they try to leave," Porter said. "Actions like these demonstrate why Russia did not belong on the U.N. Human Rights Council, and they also reinforce the U.S. assessment that members of Russian forces are committing war crimes in Ukraine."

Porter declined to say if the department considers the train station attack a war crime, saying, "Assessing individual criminal liability in specific cases is the responsibility of courts, as well as other investigatory bodies. But as the secretary, Secretary [of State Antony] Blinken, has said, 'Those responsible for war crimes and other atrocities committed in Ukraine will be held to account.'"

-ABC News' Conor Finnegan