By Jennifer Hauser and Jeevan Ravindran, Feb. 26 (CNN): The United Nations Deputy High Commissioner for Refugees, Kelly Clements, told CNN that up to 4 million people could try to cross borders as the crisis in Ukraine continues.

Speaking to CNN's Michael Holmes on Saturday morning from the Swiss capital Geneva, Clements said people were having to make "life or death decisions," with 850,000 people internally displaced while over 120,000 people had fled Ukraine.

Clements said there were queues at a number of border crossings, and many Ukrainians were monitoring the situation. She added that "many more" would follow the "large number" of refugees who have already crossed into neighbouring Moldova.

"We now see over 120,000 people that have gone to all of the neighbouring countries. And I have to say, the reception that they are receiving from local communities, from local authorities, is tremendous," Clements said. "But it's a dynamic situation, we're really quite devastated obviously with what's to come, and we would say that up to 4 million people could actually cross borders if things continue to deteriorate, which they have until now."
The latest estimate of displaced people is a huge increase from numbers cited by United Nations High Commissioner for Refugees Filippo Grandi on Friday when he said more than 50,000 people had fled Ukraine in the previous 48 hours.

Refugees from Ukraine arrive in Medyka, Poland, after crossing the border from Shehyni in Ukraine on February 25. (Michael Kappeler/picture alliance/Getty Images)

The Deputy High Commissioner for Refugees called for the protection of civilians and civilian infrastructure, saying, "international humanitarian law demands it" and people's lives were "quite literally being taken in this conflict."

"So far those borders are open, and this is something that's tremendously important in a dynamic situation like this," Clements added.