Pope Leo criticised the emergence of nationalist political movements on Sunday, calling them unfortunate, without naming a specific country or national leader.

Leo, the first pope from the U.S., asked during a Mass with a crowd of tens of thousands in St. Peter's Square that God would "open borders, break down walls (and) dispel hatred."

"There is no room for prejudice, for 'security' zones separating us from our neighbours, for the exclusionary mindset that, unfortunately, we now see emerging also in political nationalisms," said the pontiff.

Leo, the former Cardinal Robert Prevost, was elected on May 8 to succeed the late Pope Francis as leader of the 1.4-billion-member Church.

Before becoming pontiff, Prevost was not shy about criticizing U.S. President Donald Trump, sharing numerous disapproving posts about Trump and Vice President JD Vance on X in recent years.

The Vatican has not confirmed the new pope's ownership of the X account, which had the handle @drprevost, opens new tab, and was deactivated after Leo's election.

Francis, pope for 12 years, was a sharp critic of Trump. The late pope said in January that the president's plan to deport millions of migrants in the U.S. during his second term was a "disgrace."

Earlier, Francis said Trump was "not Christian" because of his views on immigration.

"A person who thinks only about building walls, wherever they may be, and not building bridges, is not Christian," Francis said when asked about Trump in 2016.

Leo was celebrating a Mass for Pentecost, one of the Church's most important holidays.