Pope Francis on Friday lamented continued persecution against Christians and other religious believers, encouraging scholars and governments to defend religious liberty.

"Nowadays, persecution against Christians is stronger than it was in the first centuries of the Church, and there are more Christian martyrs than in that time," the Pope said June 20 in the Vatican's consistory hall will participants of the conference "International Religious Liberty and the Global Clash of Values."

The June 20-21 conference being held in Rome is co-sponsored by the School of Law at St. John's University in New York and by the law department at Rome's Università Maria SS. Assunta.

Pope Francis said it is "incomprehensible and worrisome" that there continue to be discrimination and restrictions of rights on the sole basis of religious profession. He said persecution motivated by religious affiliation is "unacceptable."

"It gives me great pain to see that Christians around the world suffer the most from such discrimination."

Research institutions such as the Pew Research Center have found that religious hostilities involving religion reached a six-year high in 2012, while government restrictions on religion have increased in Europe, the Middle East, and North Africa.

In his comments to religious liberty scholars, Pope Francis reflected on Catholic teaching, citing the Second Vatican Council's declaration on religious freedom, "Dignitatis humanae."

"Every human is a 'seeker' of truth on his origins and destiny," the Pope said. "In his mind and in his 'heart,' questions and thoughts arise that cannot be repressed or stifled, since they emerge from the depths of the person and are a part of the intimate essence of the person. They are religious questions, and religious freedom is necessary for them to manifest themselves fully."

He called religious freedom "a fundamental right of man." It is "not simply freedom of thought or private worship," but "the freedom to live according to ethical principles, both privately and publicly, consequent to the truth one has found."

"Legal systems, at both national and international level, are therefore required to recognize, guarantee and protect religious freedom, which is a right intrinsically inherent in human nature."

Religious freedom is also "an indicator of a healthy democracy" and "one of the main sources of the legitimacy of the state," the Pope continued.

Pope Francis said that the globalized world also faces a "great challenge" and a "sickness" in which "weak thought even reduces the general ethical level, in the name of a false concept of tolerance that ends up persecuting those who defend the truth about humanity and its ethical consequences."

The Pope told the religious liberty conference participants that he hoped they would show with depth and rigor the reasons that religious freedom should be respected and defended.