Russia invaded Ukraine on Feb. 24, and conditions have been unsafe for civilians in Kyiv and other areas of the country. | Wikimedia Commons/Sgt. Alex Skripnichuk

Bishop David Ricken of the Green Bay Diocese joined the call for peace in Ukraine.

"The people of Ukraine. The people of Russia. All people everywhere! Our prayers are for all involved in conflict worldwide," he tweeted. "War is a defeat for all, while peace is a true victory for every person in every nation, everywhere."

The Russian military invaded Ukraine on Feb. 24 and has been mounting attacks against the country from the north, south and east, CNBC reported. If Russia establishes even "patchy" control of Ukraine, "analysts predicted refugee flows of five million to 10 million people from Ukraine to Western Europe, the story said.

More than two million Ukrainians fled their country within the first 12 days of Russia's invasion, according to NPR.               

Pope Francis has repeatedly called for peace in Ukraine, tweeting on March 6, "I make a heartfelt appeal for humanitarian corridors to be genuinely secured, and for aid to be guaranteed and access facilitated to the besieged areas, in order to offer vital relief to our brothers and sisters oppressed by bombs and fear. I thank all those who are taking in refugees. 

"Above all, I implore that the armed attacks cease and that negotiation - and common sense - prevail. And that international law be respected once again!" 

Bishop Ricken also tweeted on March 5: "In a world hell-bent on war, we are called to be a people heaven-bent on peace."