Russia-Ukraine updates: Putin says 'certain positive movements' in negotiations

Samaritan’s Purse opened an outpatient clinic just outside the train station in Lviv on Thursday and has already treated its first patients.

Some people have evacuated so quickly they left their homes without their medicine -- and by the time they made it to Lviv they were in desperate need, Mark Agness, an emergency room doctor from California, told ABC News. Pregnant women and newborns are also common.

"That’s why we do this … it’s really the parable of the Good Samaritan. Help thy neighbor -- well they’re my neighbor," said Agness.

Chelsea Musick, a nurse from Iowa, has been with the organization for years and said working in Ukraine is different. Unlike other humanitarian disasters, this was entirely man made, she said. She described the patients she’s seeing as having a "haunted" look in their eyes.

Samaritan’s Purse is also building a large field hospital, which they expect to be operational by the weekend, in the parking garage of a local mall, a few minutes away from the train station. The hospital will have enough room for 15 surgeries a day and will be able to increase beds as needed.

The operation is primarily funded by individual donors from the U.S., the organization said. Two airlifts of supplies have already been coordinated from the U.S.

-ABC News' Irene Hnatiuk, Maggie Rulli and John Templeton

In a college gym-turned-shelter, Kyrill Nodikov, a Ukrainian poet who has been published in Ukraine and Russia, told ABC News he and his 20-year-old son are ready to enlist in the war.

Nodikov was seeking refuge in a shelter with his wife, their three kids, a dog and a tabby cat.

There are thousands of families struggling with the same dilemma: whether to take their animals, which makes their exodus far more complicated, or leave them behind. Most have stayed loyal to their animals.

When asked what it would be like to take care of her twins and pets by herself, Oksana, Nodikov's wife, started crying.

Sitting on mats on the floor of the gymnasium, the family gathered in a huddle, hugging, holding and comforting Oksana. And then they did the Ukrainian version of a pinky promise: hooking their pinkies and saying, “Peace, friendship, bubble gum."

-ABC News' Matt Gutman, Brandon Baur and Scott Munro

Russia-backed forces have allegedly seized several neighborhoods in Mariupol amid an ongoing operation to "liberate" the southeastern Ukrainian port city.

"The operation to liberate the city of Mariupol of nationalists has been continuing," Russian Ministry of Defense spokesman Igor Konashenkov said at a press briefing. "Donetsk People's Republic militia units have taken control of the neighborhoods of Azovsky, Naidenivka, Lyapyne, and Vynohradar and approached the Azovstal plant. The western neighborhood in the western part of the city has been liberated."

The self-declared Donetsk People's Republic is one of two Russia-controlled separatist areas in eastern Ukraine's Donbas region.

A "small number" of soldiers from the United Kingdom may have "disobeyed orders" by joining Ukraine's fight against invading Russian forces, according to a spokesperson for the British Army.

"We are aware of a small number of individual soldiers who have disobeyed orders and gone absent without leave, and may have travelled to Ukraine in a personal capacity," the British Army spokesperson told ABC News in a statement Wednesday night. "We are actively and strongly encouraging them to return to the U.K."

Personal information on the individuals is not being released for privacy reasons, according to the spokesperson.

The U.K. is advising against all travel to Ukraine and warned that going to fight or assist others engaged in the conflict may be against the law or could lead to prosecution. The U.K., along with its allies, is providing a range of support to Ukraine, including enhancing the country's defense capability. But that support is fundamentally defensive in nature and neither NATO nor Ukraine pose any aggressive threat to Russia, according to a spokesperson for the U.K. Ministry of Defense.

"All Service Personnel are prohibited from travelling to Ukraine until further notice," the U.K. defense ministry spokesperson told ABC News in a statement. "This applies whether the Service Person is on leave or not. Personnel travelling to Ukraine will face disciplinary and administrative consequences."

The spokesperson noted that the U.K. has incredibly limited consular support in Ukraine and is unlikely to be able to offer assistance to any citizens there. There are many ways people can support Ukraine, including through charitable donations, according to the spokesperson, who acknowledged the strong desire to want to help defend freedom and democracy in Europe.

-ABC News' Guy Davies