A military spokesman said the operation would cover large parts of Sinai plus parts of the Nile delta and the western desert, where other militants have waged attacks.
Egypt’s president, Abdel Fattah al-Sisi, a former general, ordered the military to defeat militants in north Sinai within three months after an attack on a mosque in November killed 300 people, the deadliest such incident in the Arab world’s most populous country.
Sisi posted on his Facebook account on Friday: “I follow with pride the heroic actions of my sons in the armed forces and police to clear Egypt’s territory of terrorist elements.”
The offensive, which involves the army, navy, air force, border patrol and police, takes place weeks before the presidential election in which Sisi is seeking a second term. He is running virtually unopposed and set to win comfortably, despite anger over austerity measures and persistent unemployment. The success or failure of the military offensive will most likely not affect the result.
Sinai has been under a state of emergency since October 2014, when Islamist militants killed more than 30 soldiers in a single operation.
Years of fighting has failed to crush the local Islamic State affiliate, Wilayat Sinai (the governate of Sinai), which is also blamed for bombing attacks on churches in Cairo and other cities, killing dozens of Christians. The group also downed a Russian passenger jet carrying tourists back from the resort of Sharm el-Sheikh in 2015, killing 224 people.