A raid by Egyptian police on a suspected terrorist hideout in the Sinai Desert killed an unknown number of Islamists and resulted in the death of at least 50 police and conscripts.

One of the groups, Ansar Bayt al-Maqdis, is affilaited with ISIS.

Reuters:

Sources had said late on Friday at least 30 police were killed. Egypt is battling an Islamist insurgency concentrated in the Sinai peninsula from two main groups, including an Islamic State affiliate, that has killed hundreds of security forces since 2013. The interior ministry released a statement on the operation on Friday but has so far not given any details on casualties. At least 23 police officers were killed and the other victims were conscripts, the sources said. Security sources on Friday said authorities were following a lead to a militant camp in the desert where eight suspected members of Hasm Movement were believed to be hiding. The group has claimed attacks around Cairo targeting judges and police. A convoy of four SUVs and one interior ministry vehicle was ambushed from higher ground by militants firing rocket-propelled grenades and detonating explosive devices, one senior security source said. Militants are mostly fighting in remote northern Sinai where the Ansar Bayt al-Maqdis group pledged allegiance to Islamic State in 2014. Attacks mostly hit police and armed forces, but militants have also targetted Egypt's Christians and tourists.

The Sinai Desert is a vast expanse in northwestern Egypt that is lightly populated. It is the perfect hideout and training area for terrorists, who have been growing in strength in the last two years despite a determined effort by Egyptian president el-Sisi to reclaim the lawless frontier.

El-Sisi's predecessor, the Muslim Brotherhood's Mohammed Morsi, neglected security in the region, allowing terrorists to gain a foothold. Now small groups of terrorists swoop down on detachments of police and the army in hit-and-run attacks. They also carry out attacks that target the dwindling number of Christians in Egypt as well as foreign tourists.

ISIS in Egypt may be gaining recruits who have left Syria in search of more fighting. That's the concern of Israel about terrorists in Sinai:

As the war against Islamic State in Syria appears to be drawing to a close, Israeli intelligence officials fear that many ISIS fighters might choose to go to the Sinai Peninsula and join the group's affiliate there, which – despite its small size – is considered by many to be one of the most effective ISIS branches carrying out numerous deadly attacks on Egyptian security forces. Israel shares a 240-km. border with the Sinai, and Jerusalem and Cairo share an interest in the fight against the insurgents in the desert peninsula. According to Islamic State, Israel has carried out strikes against its positions. According to Oded Berkowitz, regional director of intelligence – Africa division at MAX-Security Solutions, foreign press have reported that Israel is helping the Egyptian military against terrorists in the Sinai Peninsula. Earlier on Sunday, several Egyptian military checkpoints were attacked by Islamic State insurgents, killing six soldiers and wounding another 37. According to Egyptian authorities quoted by Reuters, the checkpoints in northern Sinai were attacked by some 100 ISIS terrorists using car bombs, rocket-propelled grenades and other light weapons. According to Berkowitz, the rise in attacks against Egyptian military personnel is due to the increased pressure felt both by ISIS in Iraq and Syria as well as its Sinai affiliate. "When cornered and desperate they turn to more extreme measures.

Egypt has a large, well trained army but apparently insists on treating its Sinai problem – at least in part – as a law enforcement matter. I suspect that this will change as Egypt's ISIS problem becomes a headache not only for them, but for Israel as well.