The remarks come during a period of heightened tension in Egypt between the majority Muslims and a Christian minority that feels discriminated against.

Shenouda's apology comes a day after the premier institute of Islamic learning in the Sunni Muslim world, Al-Azhar, criticized Bishop Bishoy, the Coptic Church's No. 2, for provoking sectarian tension.

Bishoy was quoted in the Egyptian media for wondering about the time frame for the revelation of the Qur'anic verses disputing the divine nature of Jesus Christ. The bishop reportedly said these verses were inserted after the Prophet Muhammad's death by one of his successors.

Tensions between Muslims and Copts are on the rise over issues like the construction of new churches and bitter arguments over conversions. The two communities generally live in peace, though clashes and attacks have taken place.

"Debating religious beliefs are a red line, a deep red line," Shenouda said in an interview aired on state-run TV. "Maybe they (Bishoy's address) thought this is for priests only and the remarks were not for publication." "I am sorry if our Muslim brother's feelings were hurt," he added.

Bishoy also sparked outrage last week when he told Al-Masry Al-Youm newspaper that "Muslims are only guests" in the country.

For this incident, Shenouda blamed the press for possibly misquoting Bishoy and said that "we are the ones who are guests since Muslims are the majority." Coptic Christians make up around 6 to 10 percent of the country's 80 million people. Prior to the 7th Century Arab invasion, Egypt was majority Christian.

Thousands of Muslims demonstrated on Friday against Bishoy's remarks and Al-Azhar's Islamic Research Center held an emergency meeting to condemn the bishop's statements.

"Such irresponsible statements threaten ... national unity at a time when it is vital to maintain it," said the statement.

The leader of the Muslim Brotherhood opposition group, Mohammed Badie, urged Muslims to "respond to whomever slanders the book of God or the prophet." Shenouda appealed for calm.

"You don't extinguish fire by adding more fire, you need water," he said.

Seeking to cool the controversy, political parties and the journalists' association have urged their members to stay away from the debate.