( CNN ) -- A car bomb exploded Wednesday in Egypt 's restive Sinai region , killing 10 soldiers and injuring 31 others who were on their way to the capital on leave . State media reports said a suicide bomber set off the blast as two minibuses carrying infantry soldiers were passing by . Last month , a suicide bomber blew up a car in Egypt 's Sinai , killing four security officers and wounding four others . And a bombing that targeted a military intelligence building bordering on the Sinai , wounded at least six soldiers . No claim of responsibility has been reported in Wednesday 's attack . Islamist militants have become more active in the Sinai in recent years . The Egyptian revolution of 2011 that toppled strongman President Hosni Mubarak brought a resurgence of Islamists whom his military regime had repressed for decades . This included more moderate factions like the Muslim Brotherhood , which swept into power when Mohamed Morsy became President in Egypt 's first democratic elections . But it also included extremists , some suspected of having affiliations with al Qaeda . In the Sinai , they called for the establishment of an Islamist caliphate . The Egyptian military began cracking down on them again . In July , when the military ousted Morsy in a coup , Islamist extremists in the Sinai saw it as an attack against Islam and have stepped up their assaults , particularly against soldiers and military installations . Egypt 's Morsy says he 's still the legitimate president . CNN 's Saad Abedine contributed to this story .
The soldiers were headed to the country on leave . Islamist militants have declared an Islamic State in Egypt . They have stepped up their attacks on Egyptian soldiers , since Mohamed Ali was deposed .