North Korea on Monday reportedly fired three ballistic missiles off its eastern coast while its diplomatic ally was hosting the G20 Summit, South Korean military officials said. The incident is being viewed as a display of strength, as the isolated country has dismissed the United Nations Security Council-imposed ban on its ballistic missile-related activities, Reuters reported. North Korea views the ban as an infringement on its right to self defence.

According to the news agency, South Korea's Office of the Joint Chiefs of Staff said the missiles entered Japan's air defence identification zone. Responding to the announcement, Japan's Defence Ministry said, "We are still analyzing details but this is a grave threat to our nation's security, and we express deep concern."

The missiles were launched a few hours after the leaders of South Korea and China met on the sidelines of the G20 summit in Hangzhou. South Korean President Park Geun-Hye and Japanese Prime Minister Shinzo Abe met after the missile launches, and decided to collaborate on dealing with the situation, a statement released by the Abe government said.

Seoul said the missiles were medium-range Rodong-class, The Guardian reported. According to a BBC report, the North fired a ballistic missile from a submarine to display its displeasure over the US and South Korea's annual military exercises two weeks ago.

South Korean president Park Geun-Hye told Chinese President Xi Jinping that Pyongyang's fourth nuclear test and missile launches posed a threat to Seoul's ties with Beijing. Xi told the leader that China was committed to achieving the denuclearization of the Korean peninsula, Xinhua reported. Xi also expressed China's opposition to Seoul's Terminal High Altitude Area Defense System, which South Korea claims is aimed at countering North Korea's missile threat.