Gunmen killed 21 Egyptian military border guards near the frontier with Libya on Saturday, highlighting a growing threat from an area that security officials say has become a haven for militants seeking to topple the Cairo government. Security officials said the assailants were smugglers. But an army spokesman said on his Facebook page that “terrorists” – the term authorities use to describe Islamist militants – were behind the attack. He said a weapons storage facility was blown up by a rocket-propelled grenade in an exchange of fire, killing the soldiers and wounding four others. The attack took place in Wadi al-Gadid governorate, which borders both Sudan and Libya. Two smugglers were killed in clashes with the guards, security officials said. Egyptian President Abdel Fattah al-Sisi has repeatedly expressed concerns about militants who have capitalized on the chaos in Libya and set up operations along the border. […]