The US and South Korea have staged a joint missile exercise - in response to the North's latest missile test.
North Korean leader Kim Jong Un has said the second test of North Korea’s intercontinental ballistic missile has demonstrated his country can hit the US mainland.
China has urged all sides to show restraint - but criticised Pyongyang for what it calls a breach of UN security council resolutions.
Analysts think major American cities - like Chicago and Los Angeles - could now be within reach of North Korea’s missile.
Sky's Asia correspondent Katie Stallard said a night launch is unusual.
“What we normally see is missile tests happening shortly after dawn,” said Stallard.
“This is a new tactic” she added, suggesting that they may be experimenting, using the cover of darkness for these activities.