Photos and videos show long waits, traffic jams at border crossings as thousands try to leave Ukraine

More than a half-million people have crossed into neighboring countries since the start of the conflict, the U.N. High Commissioner for Refugees said Monday. More than half have gone to Poland, the refugee agency said, and people are also streaming into Moldova, Slovakia, Romania and Hungary.

Traffic data from Google showed severe backups at nearly every border crossing Sunday at 10:25 pm local time, particularly at crossings into Poland, where thousands of people are still waiting to leave. Google has since temporarily disabled live traffic data in Ukraine, amid fears for the safety of local communities. Ukrainians trying to leave by train and bus also struggled with crowds and service halts.

Officials warn that the flow of refugees is likely to escalate into a full-blown humanitarian crisis.

On Sunday, Ylva Johansson, the European Union’s home affairs commissioner, said member nations need to be prepared to support “millions” of Ukrainians in the coming months.

Ukrainians can stay, visa-free, for 90 days in E.U. nations, and Johansson said the E.U. will request member nations next week to grant asylum to Ukrainians coming to Europe for up to three years.

“The tidal waves of suffering this war will cause are unthinkable,” U.S. Ambassador to the United Nations Linda Thomas-Greenfield on Wednesday said, saying that up to 5 million Ukrainians — roughly 10 percent of the population — could become refugees if Russia’s assault continues.

If that scale of exodus holds, this will be Europe’s worst humanitarian emergency since 2015, when more than 1 million people were displaced from Syria, Iraq and Afghanistan.

More than 280,000 people had crossed into Poland as of Monday, according to the country’s border guard. In total, the country is expected to receive up to 1 million refugees.

Lines of cars stretched for 20 miles from the border crossing into Medyka, Poland, on Sunday one of the busiest posts between the two countries.

Slovakia declared a state of emergency Saturday morning because of the mass influx of foreigners caused by the war. The government approved an infrastructure bill of 13 billion euros to strengthen the Ukrainian border infrastructure and complete asylum facilities.

Nearly 80,000 Ukrainians have crossed into Hungary, according to border police.

Satellite images provided by Maxar show a four-mile-long line at the border crossing in Siret, Romania, on Friday. Romania’s border police said some 43,000 Ukrainian citizens crossed the border in the first three days of the conflict. The Romanian defense minister said earlier this week that the NATO country of 19 million could take in up to 500,000 refugees.

Moldova’s border police said Monday that nearly 70,000 Ukrainian citizens had entered the country since Feb. 24, with the largest flows were coming from the Criva and Palanca crossings.

As conflict intensified, Ukraine’s border guards were ordered Friday to stop all male citizens between the ages of 18 and 60 from leaving the country, disappointing many who got to border checkpoints after hours of travel and wait.

“If I could go, too, I would,” Vitali, 31, told The Washington Post after his wife and child crossed into Poland, with tears in his eyes. “It’s brutal.”

Leslie Shapiro and Monica Ulmanu contributed to this report.