ISIS claimed responsibility for the attack on a police checkpoint several hundred metres (yards) from the entrance to the monastery, one of the world's most important Christian sites.
The attack comes just 10 days before Pope Francis is scheduled to visit Egypt and just over a week after two deadly suicide bombings on Christian churches, also claimed by Islamic State, plunged the country into mourning and marked one of the bloodiest days for the country's Christian minority in decades.
St. Catherine's, founded in the 6th century and located at the foot of Mount Sinai, is one of the oldest Christian monasteries in the world and a UNESCO world heritage site. It is part of the Eastern Orthodox church.
Egypt's Christian minority, which makes up about 10 percent of the country's 92 million people, has increasingly been targeted by Islamist militants, with three deadly church attacks in the span of four months.
In February, scores of Christian families and students fled North Sinai province after a spate of targeted killings.
Egypt has for years been battling an Islamist insurgency in the rugged and thinly populated northern Sinai, which gained pace after the military overthrew President Mohamed Mursi of the Muslim Brotherhood in 2013 following mass protests against his rule.
Attacks in Egypt's southern Sinai, a popular destination for tourists dotted with Red Sea resorts, are by contrast rare.
Israel took the unusual step earlier this month of barring its citizens from crossing into the Sinai peninsula, saying the threat of attacks in the area inspired by Islamic State and other jihadi groups was high.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)