Sting lashed out at world leaders on Saturday calling them "cowards" for failing to resolve the refugee crisis, praising, however, the role of Greece.

"Thank God for Greece because you have shown the way," Sting said, at an Amnesty International event in Athens ahead of his performance on Saturday night.

"You have shown how to treat refugees when other people are building walls. When children are being taken from their mothers and put in cages, you are acting with compassion and generosity and commonsense," he said, according to Athens News Agency.

On Wednesday US President Donald Trump ordered an end to the family separations which have sparked domestic and global outrage but the fate of the more than 2,300 separated children in the US has remained unclear.

Sting, who recently brought his stage musical The Last Ship to Dublin, added, "Because our so-called leaders, a sad parade of half-men, cowards, have not got the solutions. Democracy began here in Greece, you are showing us how to be civilised again".