Mgr Alfred Xuereb was appointed bishop by Pope Francis in a ceremony at the Vatican.

In his homily, Pope Francis cautioned bishops to avoid politicking, business and high society.

Francis elevated to bishops' rank three priests during a ceremony in St Peter's Basilica on Monday evening.

He said bishops should "abandon the temptation to become princes," and that they are tasked "more with serving than dominating." He told them to be available to priests in their jurisdiction "the same day, or at most, the next day" after being sought.

Francis told the three they were chosen "not for business, not for high society, not for politics." In his five years as pope, Francis has insisted clerics must serve the rank-and-file and avoid seeking glory.

The new bishops are: Monsignors Waldemar Stanislaw Sommertag from Pelplin diocese, Poland; Alfred Xuereb, Gozo diocese, Malta; and Jose Avelino Bettencourt, Ottawa archdiocese in Canada.

Monsignor Alfred Xuereb, former second secretary of Benedict XVI and for some months also of Pope Francis, will take up a new appointment in South Korea.