U.S. President Donald Trump issued a stark warning to North Korean leader Kim Jong Un on Wednesday, telling him that the nuclear weapons he is developing "are not making you safer, they are putting your regime in grave danger."

"Do not underestimate us and do not try us," Trump told North Korea as he wrapped up a visit to South Korea with a speech to the National Assembly in Seoul.

In a wide-ranging address that lodged specific accusations of chilling human rights abuses against Pyongyang, Trump used some of his toughest language yet against North Korea, calling on countries around the world to isolate Pyongyang by denying it "any form of support, supply or acceptance."