Trump: US opioid epidemic 'a national emergency'

US President Donald Trump has declared addiction to opioid painkillers in the US a national emergency and says his administration is drawing up plans to tackle it.

Answering a reporter's question, he described it as "a serious problem, the likes of which we have never had".

The number of deaths from the drugs, which were prescribed to a third of Americans in 2015, has quadrupled in 20 years.