Thousands of Egyptians are mourning the death of Pope Shenouda III, the longtime leader of the Coptic Orthodox Church, who died March 17 at the age of 88.

His funeral will be today (March 21) at St. Mark's Cathedral in Cairo, where his body has been sitting in state on a large wooden throne.

Tributes have come in from around the world, with Pope Benedict XVI offering prayers and U.S. President Barack Obama praising Pope Shenouda as an “advocate for tolerance and religious dialogue.”

Shenouda, the 117th Patriarch of Alexandria, ruled for 41 years amid great political turmoil. A supporter of former Egyptian president Hosni Mubarak, he was an outspoken advocate for Christians in a predominantly Muslim nation.

“His ecumenical contributions are remarkable,” the Rev. Setri Nyomi, general secretary of the World Communion of Reformed Churches, said in a statement. “He was a prophetic leader who understood the historic impact of the Coptic Church for centuries and what the church is called upon to do now to make a difference in the existential situation in Egypt and in the entire world.”

World Council of Churches General Secretary the Rev. Olav Fykse Tveit paid tribute to Pope Shenouda’s unwavering pursuit of Christian unity and peace throughout the Middle East and the world.

“As a leader he taught us that modesty is the best way to serve Christ,” wrote Tveit, noting that Shenouda is remembered as “a strong believer in Christian-Muslim conviviality and cooperation. His initiatives in the field of inter-religious dialogue contributed to the unity of the Egyptian people.”

Shenouda worked as a journalist before becoming a monk. In the 1980s, he spent more than three years in exile in the desert monastery of St. Bishoy, after then-President Anwar Sadat stripped him of his powers for criticizing violence against Copts by Islamic extremists. Copts make up about 10 percent of Egypt’s population.

Mubarak freed Shenouda in 1985 in time to lead Christmas Mass before a crowd of thousands in St Mark’s Cathedral.

In accordance with his wishes, Shenouda will be buried at St. Bishoy. Egypt’s ruling military council said a military transport plane will take Shenouda’s body from Cairo to St. Bishoy after the funeral, the English-language Ahram Online reported.

Coptic leaders say there is no timetable to pick Shenouda's successor.