Pope Francis will visit the Greek island of Lesbos on 16 April to meet migrants, in a sign of concern about Europe’s handling of the crisis.
The Vatican said the Pope had been invited to Lesbos by the Eastern Orthodox Patriarch, Bartholomew I.
It was a gesture of “solidarity” with migrants – many of them Syrian refugees – in a “difficult, dramatic situation” in the region, the Vatican said.
Greece has started deporting migrants to Turkey – a policy backed by the EU.
Migrants who do not apply for asylum or whose claim is rejected are now liable to be deported. But there are concerns that victims of war and persecution, entitled to international protection, may be among them.
More than a million migrants have reached Greek islands from Turkey since January 2015, most having risked their lives aboard flimsy, overcrowded boats. It has become a lucrative business for people smugglers.
In 2013 Pope Francis visited the tiny Italian island of Lampedusa which, like Lesbos, has struggled with a huge influx of migrants. At the time, the boatloads from strife-torn Libya were the focus of the crisis.
The Pope has also spoken out against persecution of Christian minorities by Islamist extremists in Iraq and Syria, where fighting has forced millions to flee to neighbouring countries.