At least 20 Islamic State militants were killed over the past 24 hours as security forces started military operations in Nangarhar province of Afghanistan, an official said on Sunday.The forces targeted the IS hideouts in Kot and Achid districts of Nangarhar, a militant stronghold, on Saturday, Xinhua news agency reported.However, the official did not comment on the casualties of security forces.The IS militant group has not commented either yet.Nangarhar province with Jalalabad as its capital, 120 km east of Kabul, has been the scene of increasing IS activities since early last year.