US Secretary of State Hillary Clinton says the world has a duty to respond to the sinking of a South Korean warship that has been blamed on North Korea. <br/><br/>Clinton made the remarks today in Seoul, where she held brief talks with South Korean President Lee Myung-bak and Foreign Minister Yu Myung-hwan. She called the deadly March 26 attack on the Cheonan a "provocation" which requires a strong but measured response. <br/><br/>Clinton also called on China to carefully study all documents relating to the sinking of the Cheonan so it can really understand the details.<br/><br/>Forty-six South Korean sailors were killed when the Cheonan exploded and sank. An international investigation showed the ship was struck by a North Korean-made torpedo. <br/><br/>North Korea denies responsibility for the incident and the dispute about the sinking has prompted Pyongyang to sever all relations with its neighbor.<br/>Earlier today, North Korea said that it had shut down its maritime communications links with South Korea, following Tuesday's announcement that it will have no ties with Seoul while South Korean President Lee Myung-bak is in office.<br/><br/>North Korea also announced it would block road traffic to a joint industrial estate across the heavily armed border if South Korea resumes propaganda broadcasts to the North.<br/><br/>Meanwhile, Russian lawmakers told media measures needed to be taken to calm tensions on the Korean Peninsula. Chairman of the International Affairs Committee of the Federation Council told the Itar-Tass news agency that this was the primary task of the international community and the United Nations shall play an important part in this process.