US presidential hopeful Donald Trump challenged President Barack Obama on Sunday to acknowledge that the deadly Orlando shooting was an act of Islamic terrorism or resign. A gunman attacked a gay night club in Orlando overnight, killing at least 50 people and injuring 53 more. US media reported that the attacker, Omar Saddiqui Mateen, was a US national of Afghan origin who had vowed loyalty to the Daesh terror group. "Is President Obama going to finally mention the words radical Islamic terrorism? If he doesn't he should immediately resign in disgrace!" Trump wrote on his official Twitter page. In his...