Pope Leo has criticised leaders who spend billions on wars and said the world is "being ravaged by a handful of tyrants," in unusually forceful comments during his visit to Cameroon.

Speaking during a tour of a region ravaged by a deadly insurgency, the Pontiff blasted those he said manipulated "the very name of God" for their own gain.

The remarks come just days after a high profile spat with US President Donald Trump who posted a lengthy attack on the Pope, a vocal critic of the US and Israeli military operation in Iran.

The Pope had voiced his concern about Trump's threat that "a whole civilisation will die" if Iran did not agree to US demands to end the war and open the Strait of Hormuz.

Leo, who last year became the first US-born pope, has previously also questioned the Trump administration's approach to immigration.