Image of a North Korean satellite missile test. (Source: KCNA)

South Korea's presidential office said on June 11 that it will not let down its guard even though the timeframe for North Korea's planned satellite launch has expired, as Pyongyang could conduct a launch at any time.

On the same day, Japan also announced that it would maintain its ballistic missile defense systems on alert and shoot down any object it deemed a threat to its territory.

Japan's Ministry of Defense issued a statement stating: "Japan will continue to maintain a state of alert for missile defense at the present time."

Previously, North Korea informed the International Maritime Organization (IMO) of its plan to launch a satellite-carrying rocket between May 31 and June 11. The country launched the rocket on the first day of the scheduled time, but the launch failed when the rocket fell into the Yellow Sea.

At the time, North Korea admitted that the launch had failed due to engine failure and said it would try again as soon as possible. South Korean officials warned that a second launch could still occur during that time.

North Korea claims it has the right to launch a space vehicle to put a satellite into orbit. However, some countries are concerned that this could be a test of Pyongyang's intercontinental ballistic missile technology.

Under United Nations resolutions, North Korea is banned from any use of ballistic missile technology.