A recent string of militant attacks on high-profile targets across Egypt has underscored a growing threat: the fragmented jihadist groups now competing for influence over this country’s Islamist insurgency.

Since June, Egyptian insurgents have used car bombs, suicide attacks, a prominent political assassination and the beheading of a foreign oil worker to terrorize the country. The attacks have marked the most intense period of militant activity since the homegrown insurgency began two years ago.

Instead of a single group, a cluster of independent but increasingly dangerous cells linked to al-Qaeda and the Islamic State have carried out the violence, security experts say. And rivalries between the jihadist groups are expected to spur more attacks. […]