Russian President Vladimir Putin's "special military operation” into Ukraine began on Feb. 24, with troops crossing the border from Belarus and Russia. Moscow's forces have since been met with “stiff resistance” from Ukrainians, according to U.S. officials.
Russian forces retreated last week from the Kyiv suburbs, leaving behind a trail of destruction. After graphic images emerged of civilians lying dead in the streets of Bucha, U.S. and European officials accused Russian troops of committing war crimes.
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.
Here's how the news is developing. All times Eastern.
Mar 22, 2022, 7:57 AM EDT
Pope Francis calls Zelenskyy, gets invited to Ukraine
Ukrainian President Volodymyr Zelenskyy said he received a telephone call from Pope Francis on Tuesday.
Zelenskyy made the comment at the start of his 11-minute impassioned speech to Italy's parliament via video link, after which he received a standing ovation.
Ukrainian President Volodymyr Zelenskyy addresses the Italian parliament via video link, in Rome, March 22, 2022.
Roberto Monaldo/LaPresse via AP
Ukraine's ambassador to the Holy See, Andryi Yurash, later took to Twitter to confirm the call, saying Zelenskyy had a "very promising" conversation with the pontiff and invited him to visit Ukraine.
The Vatican confirmed to ABC News that the call took place but did not offer further details.
-ABC News' Phoebe Natanson
Mar 22, 2022, 7:22 AM EDT
Several fires reported in Chernobyl Exclusion Zone
Several fires have erupted within the area around Ukraine's Chernobyl nuclear power plant, according to a press release from the Ukrainian parliament, which cited satellite images from the European Space Agency.
The Ukrainian parliament said the fires in the Chernobyl Exclusion Zone, a 1,000-square-mile restricted area of deserted land surrounding the shuttered plant, were likely caused by "shelling or arson" at the hands of Russian forces, which seized the site last month.
Mar 22, 2022, 7:06 AM EDT
Over 3.5 million refugees have fled Ukraine: UNHCR
More than 3.5 million people have been forced to flee Ukraine since Russian forces invaded on Feb. 24, according to the latest figures from the United Nations refugee agency.
A mother embraces her son, who escaped the besieged city of Mariupol and arrived at the train station in Lviv, Ukraine, on March 20, 2022.
Bernat Armangue/AP
The tally from the U.N. High Commissioner for Refugees (UNHCR) amounts to just over 8% of Ukraine's population -- which the World Bank counted at 44 million at the end of 2020 -- on the move across borders in 27 days.
More than half of the refugees are in neighboring Poland, UNHCR figures show.
-ABC News' Zoe Magee
Mar 22, 2022, 6:50 AM EDT
At least 925 civilians, including 75 children, killed in Ukraine: OHCHR
At least 925 civilians, including 75 children, have been killed in Ukraine since Russian forces invaded on Feb. 24, according to the latest figures from the Office of the United Nations High Commissioner for Human Rights (OHCHR).
Meanwhile, at least 1,496 civilians, including 99 children, have been injured, OHCHR figures show.
In Lviv, 109 empty strollers are placed outside the city council during an action to highlight the number of children killed in the ongoing Russian invasion of Ukraine, on March 18, 2022.
Alexey Furman/Getty Images
The tallies are civilian casualties that occurred in Ukraine from Feb. 24 to March 20 and have been verified by OHCHR, though the agency cautioned that the true numbers are believed to be "considerably higher."
"Most of the civilian casualties recorded were caused by the use of explosive weapons with a wide impact area, including shelling from heavy artillery and multiple-launch rocket systems, and missile and air strikes," OHCHR said in a statement late Monday. "OHCHR believes that the actual figures are considerably higher, especially in Government-controlled territory and especially in recent days, as the receipt of information from some locations where intense hostilities have been going on has been delayed and many reports are still pending corroboration."