A repatriation flight carrying between 200 and 300 migrants took off from Minsk on Thursday bound for Erbil in Iraqi Kurdistan, and Baghdad. The flight to Baghdad carried 431 people, Russia's Interfax news agency reported.

In 2015-16, more than 1 million people, primarily Syrians, poured into Europe. The resulting backlash buoyed right-wing nationalists across the continent, and since then, mainstream politicians have been reluctant to embrace immigration.

The number of migrants that have crossed or are waiting to cross the Poland-Belarus border is not so large when compared with the millions who fled Syria or Afghanistan, but the politics of migration are so volatile in Europe that even a small group can trigger tensions.

The New York Times said the right-wing governing party in Poland has long termed non-European migrants a threat to Polish culture and sovereignty, and its response to the current group has been predictably heated.

Six years ago, some countries, notably Germany, welcomed migrants, while others, including Poland, refused to accept more than a few, clashing with EU leaders. But there was no danger that the issue would develop into armed conflict.

Now, no one is offering to take the migrants, even as they experience life-threatening conditions. The EU is united behind Poland, which is portraying itself as the first line of defense for the bloc, while Warsaw and Minsk are trading ominous threats.