Emergency declared in US after 'devastating' tornado

At least 24 injured people have been taken to hospital after a "devastating" tornado hit Little Rock, Arkansas, according to the city's mayor. The twister churned through the US state's capital city on Friday, flipping cars, smashing roofs, and toppling trees.
Several blocks have been heavily damaged, according to aerial footage posted by the Weather Channel.
Nearly 90 million people in 15 US states are under threat from an "explosive" storm system.