In Seoul, a South Korean government spokesman said the explosion appeared not to be related to a nuclear test. Kawaguchi visited Beijing mainly to attend a business forum, but her talks with Tang are part of a flurry of diplomatic activity aimed at resolving differences over the talks on North Korea's nuclear programme. Li Changchun, a member of the powerful nine-member standing committee of the Chinese Communist Party's politburo, was scheduled to return to Beijing on Monday after weekend talks with North Korean leaders. U.S. Assistant Secretary of State was scheduled to travel from Tokyo to Beijing on Sunday for talks with Chinese officials on Monday, a U.S. embassy spokeswoman said. Japanese, U.S. and South Korean officials discussed the six-party talks in Tokyo last week. North Korea last month said it was "impossible" to hold another round of six-party talks because of the United States' "hostile policy". The last round of talks was held in June, involving North Korea, the United States, China, South Korea, Russia and Japan. North Korea and the United States still disagree over major issues including the form of Pyongyang's nuclear programmes, and the sequence of implementing a possible freeze and concessions from the U.S. and other countries. --SPA 1322 Local Time 1022 GMT www.spa.gov.sa/200672