Pope concluded his 3-day visit to Turkey on Sunday, calling on Muslim leaders worldwide to strongly condemn terrorism, and exhorted other religions to stop stereotyping Islam with terror.

Speaking to reporters on his return trip aboard the plane from Turkey, he condemned Islamic State insurgents several times and told reporters what he emphasized during his private talks to Turkish President Tayyip Erdogan.

"I told the president that it would be beautiful if all Islamic leaders, whether they are political, religious or academic leaders, would speak out clearly and condemn this, because this would help the majority of Muslim people," Pope Francis said in answer to a reporter's question.

"But this must come from the mouths of their leaders, from religious leaders, academic leaders, intellectuals and political leaders," he said.

He called the violence by Islamic extremists “a profoundly grave sin against God.”

Catholic Church officials have always urged Islamic leaders to speak out more forcefully against Islamic State, but the pope's words on the plane were his strongest reaction so far.

He said he understood how Muslims were offended by the stereotype that equates Islam with terrorism. He added, “no one can say that all followers of Islam are terrorists, any more than you can say that all Christians are fundamentalists.”

 He pointed out that the Koran is a book of peace--"it is a prophetic book of peace. This (terrorism) is not Islam".

Pope Francis's visit sent out a clear message of inter-religious tolerance and immediate peace in middle east. Millions of Christians have been fleeing the violence in middle east unleashed by Islamic terrorists. Many people have been killed , many churches have been destroyed and many are fleeing their countries. Turkey has taken in more than 1.5 million refugees; the Pope met with 100 Christian children and teens who fled Iraq and have taken refuge in Turkey. Pope also sent a personal envoy to northern Iraq this summer with money from the pontiff’s own charitable fund to assist relief efforts.

On the flight back to Rome, he also said he would still like to visit Iraq but won’t do so at the moment because “it would create serious problems for the authorities in terms of security.”

Ecumenical Patriarch Bartholomew I kisses the Pope during an ecumenical prayer at the Patriarchal Church of St. George in Istanbul on Saturday, November 29.

Pope Francis and Istanbul's Grand Mufti Rahmi Yaran visit the Sultan Ahmet Mosque, popularly known as the Blue Mosque, in Istanbul on November 29.