Pyongyang unveils nuclear warheads as US carrier arrives in Busan

North Korea's Supreme Leader Kim Jong-un has ordered an increase in nuclear weapons production, amid mounting tensions with the US and South Korea. Last week, Washington and Seoul wrapped up their most extensive joint military drills in years. But Pyongyang believes they were a prelude to an invasion, and has increased missiles tests and mobilisation of its strategic nuclear arsenal. Shoaib Hasan has our top story.