North Korea has launched four missiles off its east coast, according to South Korean officials.
The short-range projectiles were fired from Mount Myohyang, northeast of the North Korean capital Pyongyang, an anonymous official from the South Korean Defence Ministry said.
They added that two of the them were fired off in the morning and a further two were fired off in the afternoon. All four were directed towards the sea.
The Yonhap News agency reported that, while some of the projectiles appeared to have reached the water, some of them may have failed to travel that far, landing on North Korean land instead.
North Korea routinely launches missile and artillery tests, but it has already carried out many more this year than it has done in previous years.
The increase is thought to be related to the rule of current leader Kim Jong Un, who inherited power in 2011.
His father, Kim Jong Il, was more sparing in his use of longer-range missiles and nuclear tests, tending to use them exclusively as a tool for negotiating concessions with the outside world.
Admiral Samuel Locklear, who is in charge of American forces in Asia and the Pacific, told a Pentagon news conference on Tuesday that the world may well be becoming “numb” to North Korea's missile tests on account of their frequency.