North Korea has test-fired two more short-range missiles according to military sources in South Korea. The defence ministry in Seoul said surface-to-ship weapons were fired about 100 kilometres into the Sea of Japan.If confirmed, it would be the latest act of muscle-flexing by the North since it caused international outrage by detonating a nuclear device in May. Tensions in the region are already high. The United Nations imposed sanctions on Pyongyang for the nuclear test and a previous missile launch. The North responded with threats to attack the South and to continue boosting its nuclear arsenal. Earlier this week, the United States said it was tightening up its crackdown against companies it believes are involved in North Korea’s nuclear weapons programme. China – a key player in enforcing the UN sanctions, said it will send an envoy to six-nation talks aimed at ending the North’s nuclear ambitions.