CAIRO • Egypt’s Grand Mufti Ali Gomaa, a prominent authority on Sunni Islam, said dialogue with Islamist hardliners could help reduce militant attacks but that those who ultimately take up arms should be killed.

Gomaa said he and his fellow scholars of Islam at Cairo’s Al Azhar University had engaged hardliners in debate for the past decade—and he said the efforts had borne fruit with diminishing militant attacks in Egypt’s Nile valley.

“As long as they are not armed and threatening the population, there is hope to have dialogue,” Gomaa said in an interview. “If terrorists have taken up arms, there is no recourse but to kill them. This is clear.”

Gomaa, who was appointed by the Egyptian government, said former militants had written 20 books, which had been published in Egypt and Saudi Arabia, explaining why they had changed course. “We were able to make these youth change their minds,” he said. “Their books had a major impact on reducing terrorism.”

Egypt fought a bloody war with Islamists in the Nile Valley in the 1990s. Militants armed with guns and swords killed 58 tourists and four Egyptians at a southern Pharaonic temple in 1997 in the worst of a series of attacks. After that incident, the Gama’a Al Islamiya, which had tried to overthrow the government by force, decided on a long-term truce. Many leading members have since abandoned violence.

Alongside its security clampdown, the government also took over thousands of private mosques in the 1990s to prevent them becoming recruitment centres for Islamist opposition groups.

While attacks in the Nile Valley have dissipated, a series of bombs targetting Red Sea resorts have killed more than 100 people since 2004.