The Americans, Andy Tai Ngoc Huynh and Alexander Drueke, are both from Alabama.
Russian President Vladimir Putin's "special military operation" into neighboring Ukraine began on Feb. 24, with Russian forces invading from Belarus, to the north, and Russia, to the east. Ukrainian troops have offered "stiff resistance," according to U.S. officials.
The Russian military has since launched a full-scale ground offensive in eastern Ukraine's disputed Donbas region, capturing the strategic port city of Mariupol and securing a coastal corridor to the Moscow-annexed Crimean Peninsula.
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A look at the two leaders at the center of the war in Ukraine and how they both rose to power, the difference in their leadership and what led to this moment in history.
About 12 Russian missiles struck in and around the Kremenchuk oil refinery in central Ukraine, according to Dmytro Lunin, head of the Poltava Regional Military Administration.
No one was injured and crews have extinguished the blaze, Lunin said.
Most missiles hit the infrastructure of the refinery, which is not operating, Lunin said.
-ABC News' Irene Hnatiuk and Yuriy Zaliznyak
The United Nations said it's verified the deaths of nearly 100 children in Ukraine in April alone -- and officials believe the actual figure to be considerably higher.
"More children have been injured and faced grave violations of their rights, millions more have been displaced," UNICEF Deputy Executive Director Omar Abdi said at Thursday's U.N. Security Council meeting. "The war in Ukraine, like all wars, is a child protection and child rights crisis."
Education also "came to a standstill" when Russia invaded, Abdi said.
One in every six UNICEF-supported schools in eastern Ukraine was damaged or destroyed as of last week, Abdi said.
"These attacks must stop. All parties must honour their legal and moral obligation to protect civilians and civilian infrastructure, to respect international humanitarian and human rights law, and to ensure the rights of children are upheld," Abdi said.
-ABC News' Christine Theodorou
"Difficult" negotiations are underway between Ukraine and Russia to coordinate the evacuation of seriously wounded fighters from the Azovstal steel plant in Mariupol in exchange for an unspecified number of Russian prisoners of war, Ukrainian Deputy Prime Minister Iryna Vereshchuk said.
"We are currently negotiating only 38 severely wounded fighters that can't walk," she said.
-ABC News' Irene Hnatiuk
Russia "will be forced to take retaliatory steps both of military-technical and of other nature in order to stop the threats to its national security" in response to Finland’s possible accession to NATO, according to state-run TASS citing a statement by the Russian Foreign Ministry.
The ministry added, "Finland joining NATO will seriously harm bilateral Russian-Finnish relations and the maintenance of stability and security in the North European region."
