Japan's military is on alert for a possible North Korean ballistic missile launch, a government source said, with local media reporting its navy and anti-missile division have been told to shoot down any projectile heading for Japan.

North Korea appeared to have moved an intermediate-range missile to its east coast, but there were no signs of an imminent launch, South Korea's Yonhap News Agency reported, citing an unnamed government source.

A South Korean defence ministry official said it could not confirm the Yonhap report and said the military was watching the North's missile activities closely.

Tension in the region has been high since isolated North Korea conducted its fourth nuclear test in January and followed that with a satellite launch and test launches of various missiles.

Japan has put its anti-ballistic missile forces on alert several times this year after detecting signs of missile launches.

The Japanese government source said there were again signs North Korea might be preparing a launch of the intermediate-range Musudan missile, the same missile it attempted to launch in May, prompting the order for the military to go on alert.

Inside the daily life in North Korea Show all 19 1 /19 Inside the daily life in North Korea Inside the daily life in North Korea People reading a newspaper at the metro station Inside the daily life in North Korea Thoughts of the leaders on the tram. They have about a dozen of these on every tram, all with different thoughts Inside the daily life in North Korea Young people training for a big upcoming festival Inside the daily life in North Korea People at the Pyongyang's annual marathon Inside the daily life in North Korea Many stars on one of the trolleys in Pyongyang Inside the daily life in North Korea An intimidating poster in a primary school in North Korea. Inside the daily life in North Korea Solar panels installed on a street lamp. Inside the daily life in North Korea A poster on the window next to one of the venues we visited in Pyongyang Inside the daily life in North Korea Kids playing football next to the Arch of Triumph. After a while tourists were allowed to join, so some of us did Inside the daily life in North Korea Class in an educational center in Pyongyang (where people over 17 years old can attend any classes they choose after school, for free) Inside the daily life in North Korea People waving at me during the Pyongyang marathon Inside the daily life in North Korea People having a great time dancing at a public park Inside the daily life in North Korea A metro driver in a metro station in Pyongyang Inside the daily life in North Korea Fireworks to mark the birthday of the Eternal President Kim Il Sung on our last night in Pyongyang Inside the daily life in North Korea My wonderful tour guide at a public park Inside the daily life in North Korea One of the parks in Pyongyang Inside the daily life in North Korea A person rowing some boats for the day at a river in Pyongyang Inside the daily life in North Korea The National War Museum Inside the daily life in North Korea Public park in Pyongyang

South Korea's Foreign Ministry said if the North goes ahead with a launch it would again be in violation of UN resolutions and defying repeated warnings by the international community.

“It will further isolate the North from the international community,” ministry spokesman Cho June-hyuck told a briefing.

The United Nations Security Council in March imposed tightened sanctions against North Korea over its pursuit of nuclear weapons.

North Korea has failed in all four attempts to launch the Musudan, which theoretically has the range to reach any part of Japan and the US territory of Guam.

North Korea tried unsuccessfully to test launch the Musudan three times in April, according to US and South Korean officials, while a May attempt failed a day after Japan put its military on alert.

North Korea is believed to have up to 30 Musudan missiles, according to South Korean media, which officials said were first deployed in around 2007, although the North had never attempted to test-fire them until this year.