Attackers killed the worshippers who were in a packed mosque in restive North Sinai Province, making it the country’s deadliest attack in recent memory.
Witnesses say assailant surrounded the Rawda mosque with all-terrain vehicles and detonated a bomb.
Egypt’s President Abdel Fattah al-Sisi has declared three days of mourning beginning today, in remembrance of those who lost their lives.
There was no immediate claim of responsibility for the bloodshed.
The Islamic State group’s Egypt branch has killed hundreds of policemen and soldiers, and also civilians accused of working with the authorities, in attacks in the north of the Sinai peninsula.
The attack is yet another big blow for Africa as it comes less than a week after Boko Haram jihadists killed at least 50 people when a suicide bomber blew himself up at a mosque in northeast Nigeria, police said.
The blast happened during early morning prayers at the Madina mosque in the Unguwar Shuwa area of Mubi, some 200 kilometres by road from the Adamawa state capital, Yola.
Last month, at least 276 people were killed and 300 injured by a massive truck bomb that tore through a busy shopping district of Mogadishu, the government said, making it the “deadliest attack ever” to hit war-torn Somalia.