Pope Leo has said he will continue to "speak out loud" against war, after the US president launched an unusual and scathing attack over his opposition to US immigration policy and the war in Iran.

Donald Trump accused the pontiff of being "WEAK on Crime and terrible for Foreign Policy" in a Truth Social post, later telling reporters he was "not a big fan".

The Pope told reporters en route to Algeria that he did not want to get into a debate with Trump but would continue to speak out against war.

He has been a staunch critic of the Iran war, calling Trump's threat to destroy Iranian civilisation "unacceptable" and calling for him to find an "off-ramp" to end the conflict.

In general, it is rare for a pope to directly address statements by world leaders.

There are more than 70 million Catholics in the US, about 20% of the population. They include Trump's Vice-President JD Vance.

Trump's remarks came as the pontiff embarked on an 11-day trip to Africa, his second major foreign trip since being elected last year.

The US president wrote in Sunday's post that the Pope "should get his act together" and said he was "weak on nuclear weapons", apparently referring to Tehran's attempts to become a nuclear power, cited as one of the reasons for the US and Israel going to war with Iran.

He also suggested that the pontiff was elected "because he was American, and they thought that would be the best way to deal with President Donald J Trump".

"If I wasn't in the White House, Leo wouldn't be in the Vatican."

Asked by reporters later to explain the post, he said: "I don't think he's doing a very good job, he likes crime, I guess."

Trump added: "He's a very liberal person, and he's a man who doesn't believe in stopping crime, he's a man who doesn't believe we should be toying with a country that wants a nuclear weapon so they can blow up the world."

The remarks drew immediate criticism from Catholics, with one expert comparing the comments to the Pope's relationship with fascist dictators in World War Two.

"Not even Hitler or Mussolini attacked the Pope so directly and publicly," said Massimo Faggioli, quoted by Reuters.

The Pope has used numerous public addresses to denounce global conflicts and urge de-escalation in the Middle East.

When Trump threatened Iran, saying that "a whole civilisation will die tonight", he responded by saying the statement was "truly unacceptable".

In his Easter address, the pontiff said without mentioning any countries directly that people were growing accustomed to violence and indifferent to thousands of deaths.

"Let those who have weapons lay them down. Let those who have the power to unleash wars choose peace," he said.

He has also criticised Trump's hard-line immigration policy, questioning whether it was possible for someone to be "pro-life" - a term normally associated with opponents of abortion - if they agreed with what he described as the "inhuman treatment of immigrants".

Pope Leo is seen as continuing the humanitarian tradition of his predecessor Pope Francis, who said Trump was "not Christian" during the 2016 election campaign because of his anti-immigrant language.

Trump described the late Pope as "disgraceful".