Ukrainian prisoners of war (POWs) are seen during a swap at an unknown location – REUTERS Russia's most powerful mercenary group, Wagner, sent at least 100 Ukrainian prisoners of war back to Ukrainian forces to mark Orthodox Easter, according to a video posted by the group's founder, Yevgeny Prigozhin. "Prepare all of them, feed and water them, check the wounded," Mr Prigozhin was shown saying in a video posted on Telegram by his press service. A group of Ukrainian prisoners were then shown being told that they would be passed back to Ukrainian forces to mark Orthodox Easter. "I hope…