It also comes at a potentially embarrassing time for North Korea's only real ally , China, which is currently hosting the Group of Nations summit in Hangzhou

At the G20, Chinese President Xi Jinping told his South Korean counterpart on Monday that Beijing opposes the deployment of the United States' THAAD missile defense system to South Korea, according to China's official Xinhua News Agency. President Obama vowed Tuesday to toughen international sanctions against North Korea after its government conducted a test missile launch as world leaders gathered for summits in Asia. The missiles were launched from a region called Hwangju and came just hours after the leaders of South Korea and China met on the sidelines of the Group of 20 leaders' meeting in Hangzhou, China. Key points: Pyongyang's latest missile launches violate UN Security Council resolutions

Seoul has told Beijing Pyongyang's actions harm South Korea-China ties

Beijing says it is committed to a denuclearised Korean peninsula

The missiles were fired from a western region south of the capital Pyongyang, just after noon local time, South Korea's Office of the Joint Chiefs of Staff said in a statement. Speaking with reporters after a meeting here with South Korean President Park Geun-hye, Obama said that the two agreed to work “diligently together” on the most recent United Nations sanctions against North Korea to close loopholes “and make them even more effective.”

"The entire international community needs to implement these sanctions fully and hold North Korea accountable," Obama said on the sidelines of a summit of southeast Asian leaders in his last presidential trip to the continent. In March, the U.N. Security Council imposed the toughest sanctions in decades on North Korea after it began a round of nuclear and ballistic missile tests.
South Korea reports that North Korea has fired three ballistic missiles into the Sea of Japan.