Pope Leo criticised violations of international law by 'neocolonial' world powers in a forceful speech on Monday during an Africa tour, hours after U.S. President Donald Trump's direct attack on the leader of the 1.4-billion-member Church.

The first U.S. pope urged leaders in Algeria on the first day of a four-nation tour to build a society based on principles of justice and solidarity.

"Today, this is more urgent than ever in the face of continuous violations of international law and neocolonial tendencies," Leo said.

Pope Leo set off on Monday for an ambitious 10-day tour of four African countries in a bid to urge global leaders to address the needs of the continent, where more than a fifth of the world's Catholics live.

Trump’s attacks

The first U.S. pope, who was the target of an unusual, direct attack from President Donald Trump late on Sunday that drew sharp rebuke from Catholics, left Rome for Algeria, where he will spend two days.

Leo is undertaking a whirlwind tour to 11 cities and towns, traversing nearly 18,000 km (11,185 miles) over 18 flights, and will also visit Cameroon, Angola, and Equatorial Guinea.

The pope is visiting with a mission "to help turn the world's attention to Africa", Cardinal Michael Czerny, a senior Vatican official and close adviser to Leo, told Reuters.

The pope, who has emerged as an outspoken critic of the Iran war and decried the "madness of war" on Saturday, has made only one big overseas trip since being elected last May, visiting Türkiye and Lebanon in November and December. He visited Monaco in March.

Leo, aged 70, relatively young and in good health for a pope, is undertaking one of the most complicated tours arranged for a pontiff in decades.

More than 20% of the world's Catholics live in Africa, according to Vatican statistics. The three sub-Saharan nations the pope is visiting have populations where more than half identify as Catholic.