North Korea today fired a ballistic missile towards the sea off its east coast of the Korean peninsula.<br />''  <br />'' It came after a US aircraft carrier arrived in South Korea to participate in joint drills, and ahead of a planned visit by the US  Vice President Kamala Harris.<br />''  <br />'' Officials in both South Korea and Japan confirmed the launch of the missile. Seoul has described the launch as an "act of grave provocation".<br />'' <br />'' United States' nuclear-powered USS Ronald Reagan docked in the southern port city of Busan on Friday, to take part in joint drills off South Korea's east coast.<br />''  <br />'' South Korea's  President Yoon Suk-yeol, who took office in May, has vowed to beef up joint military exercises with the United States, after years of failed diplomacy with North Korea under his predecessor.<br />'' <br />'' Washington is Seoul's key security ally and stationed about 28,500 troops in South Korea to protect it from the North.<br />'' The two countries have long carried out joint exercises, which they insist are purely defensive but North Korea sees them as rehearsals for an invasion.<br />'' <br />'' Earlier this month, North Korea passed a law declaring itself to be a nuclear weapons state, with leader Kim Jong-un ruling out the possibility of talks on denuclearisation. <br />'' <br />'' Despite widespread sanctions, Pyongyang conducted six nuclear tests between 2006 and 2017.<br />