Russia-Ukraine updates: US sanctions Russian military shipbuilder, diamond miner

The U.S. Department of State announced Tuesday that it has coordinated with St. Jude Children's Research Hospital "to provide necessary life-saving and immediate care to four Ukrainian children whose ongoing cancer treatment was disrupted" by Russia's invasion of Ukraine.

The State Department helped airlift these pediatric cancer patients and some of their immediate family members from Poland to the international airport in Memphis, Tennessee, where they were subsequently transported to St. Jude Children's Research Hospital.

"There, the patients will be able to safely resume critical cancer therapy disrupted by the Kremlin’s aggression," State Department spokesperson Ned Price said in a statement. "They will receive the specialized care they desperately need, and their family members will be afforded sustenance, security, and support from St. Jude."

Over 3.5 million people have fled Ukraine since Russian forces invaded on Feb. 24, and more than half went to neighboring Poland, according to the latest figures from the United Nations refugee agency.

"Children are among the most vulnerable in a crisis, and these pediatric oncology patients need urgent and highly specialized medical care. We are proud to stand with European partners who are also treating children whose life-saving care in Ukraine has been made impossible by Putin's war," Price added. "We recognize, however, that the children transported represent a small proportion of the thousands of patients whose cancer treatment has been interrupted and, who, even amid a pandemic and with compromised immune systems, were forced to flee their homes. That is why, together with our allies and partners, we will continue to support our Ukrainian partners as we seek to save lives and bring this needless war to a close."

-ABC News' Conor Finnegan

Russian journalist Dmitry Muratov announced Tuesday that he and independent Russian newspaper Novaya Gazeta have decided to auction off their 2021 Nobel Peace Prize Medal and donate the proceeds to the Ukrainian Refugee Fund.

"There are already over 10 million of refugees," Muratov wrote on the Novaya Gazeta website, "I ask the auction houses to respond and put up for auction this world-famous award."

Muratov is the editor-in-chief of Novaya Gazeta and won the 2021 Nobel Peace Prize with journalist Maria Ressa.

Russian troops fired gas into a crowd of peaceful protesters in the southern Ukrainian city of Kherson on Tuesday.

Video from the scene, taken by journalists, shows projectiles landing in a square in central Kherson where residents had gathered to protest Russia's occupation of the city. Loud bangs can be heard and the crowd suddenly disperses as people attempt to flee the smoke and gas emitting from the canisters around them. People are seen coughing and covering their faces as they run away.

-ABC News' Julia Drozd and Fergal Gallagher

ABC News' team in Kyiv reported hearing several loud explosions just before 1 p.m. local time.

The Ukrainian capital was reported to be relatively quiet earlier Tuesday, which marks the first full day of a 35-hour curfew, set to expire Wednesday morning.

The Ukrainian Ministry of Defense said Tuesday that Ukrainian troops expelled Russian forces from Makariv, a suburb of Kyiv, after a fierce battle. However, Russian forces pushing toward Kyiv were able to take partial control of other northwestern suburbs, Bucha, Hostomel and Irpin, according to the defense ministry.