Pope Francis is urging Muslim leaders worldwide to "clearly" condemn terrorism carried out in the name of Islam.

On his way back to Rome after a three-day visit to Turkey, Pope Francis responded to a question about the Islamic State and other jihadist groups by repeating what he said he had told Turkish president Recep Tayyip Erdogan in a private meeting on Friday.

"I told him it would be wonderful if all the Muslim leaders of the world - political, religious and academic - spoke up clearly and condemned the violence which damages Islam," the pontiff said.

"That would help the majority of Muslims if that came from the mouths of these political, religious and academic leaders.

"We all have need of a global condemnation."

The pope went on to acknowledge that current global crises had generated a danger of all Muslims being tarred with the same brush.

"It is true that in the face of the acts being committed not only in this region (Iraq and Syria) but also in Africa, there is a certain reaction of repulsion, as if that is what Islam is," he said.

"I get angry, so many Muslims are offended and say 'we are not these people, the Koran is a work of peace'."

The Argentinian leader of the Catholic church also denounced what he termed the current wave of "Christianophobia" in the Middle East.

He accused Islamist radicals of "hunting" Christians, while certain officials acted as if "they did not want any left in these countries", not specifying which countries he was referring to.

Islamist violence in Syria and Iraq a 'grave sin against God'

Pope Francis was in Turkey for three days to call for great respect and tolerance between faiths.

He also specifically spoke out against Islamic militants, who have carried out "profoundly grave sins against God" in Syria and Iraq.

Turkey is sheltering nearly 2 million refugees from Syria, with thousands of Christians among them.

At a joint service with Patriarch Bartholomew I, the spiritual head of the world's 300 million Orthodox Christians, Pope Francis said people of all faiths could not remain indifferent to the cries of the victims of the "inhumane and brutal" war next door.

"Taking away the peace of a people, committing every act of violence, or consenting to such acts, especially when directed against the weakest and defenceless, is a profoundly grave sin against God," he said.

He also condemned Friday's attack on Muslim worshippers at the main mosque in northern Nigeria's biggest city, Kano, in which at least 81 people were killed.

The pope later met around 100 young refugees, mostly from Iraq and Syria, Christians and Muslims among them, and thanked Turkey for sheltering so many displaced civilians.

AFP/Reuters