CAIRO (Reuters) — Nasr Abu Zayd, an Egyptian scholar who was declared an apostate for challenging mainstream Muslim views on the Koran, died here on Monday. He was 66.

The official Egyptian news agency, MENA, said he died at a hospital where he was being treated for an unidentified illness.

Dr. Abu Zayd’s liberal, critical approach to Islamic teachings angered some Muslim conservatives in Egypt in the 1990s, when President Hosni Mubarak’s government was combating an uprising by armed Islamic militants. Dr. Abu Zayd criticized the use of religion to exert political power. He argued that the Koran was both a literary and religious text, a view that clashes with the Islamic idea that the holy book is the final revelation of God.

Islam, Dr. Abu Zayd said, should be understood in terms of its historical, geographic and cultural background, adding that “pure Islam” did not exist and that the Koran was “a collection of discourses.”

In 1995, an Egyptian Shariah court declared Dr. Abu Zayd an apostate from Islam, annulled his marriage and effectively forced him and his wife into exile. The couple moved to the Netherlands after he received death threats, notably from the Islamic Jihad group led by Ayman al-Zawahri, who has since become deputy leader of Al Qaeda.

But Dr. Abu Zayd quietly returned to Egypt in recent years, first for lectures and later for health reasons.

In reviewing his book “Voice of an Exile: Reflections on Islam” (2004), many Western academics praised his scholarship.

“Nasr Abu Zayd is a heroic figure, a scholar who has risked everything to restore the traditions of intellectual inquiry and tolerance that for so long characterized Islamic culture,” wrote Philip Jenkins, a professor of history and religious studies at Pennsylvania State University.

Dr. Abu Zayd compared Arab rulers unfavorably with leaders in Iran, Turkey and elsewhere in the Muslim world, where he said religious debate was comparatively free-flowing.

“Religion has been used, politicized, not only by groups but also the official institutions in every Arab country,” he told Reuters in 2008. The distinction between “the domain of religion and secular space,” he said, had been eroded.

“I’m sure that I’m a Muslim,” he said. “My worst fear is that people in Europe may consider and treat me as a critic of Islam. I’m not. I’m not a new Salman Rushdie and don’t want to be welcomed and treated as such. I’m a researcher.”