 South Korea agreed with the findings from the research group and President Lee Myung-bak declared afterwards that Seoul would cut all trade with North Korea as part of measures primarily aimed at striking back at North Korea diplomatically and financially.North Korea denied all such allegations and responded by severing ties between the countries and announced it abrogated the previous non-aggression agreement.On 23 November 2010, North Korea's artillery fired at South Korea's Yeonpyeong island in the Yellow Sea and South Korea returned fire.