SEOUL North Korea has fired five short-range missiles off its east coast and declared a "no sail" zone in the area from October 10-20, South Korea's Yonhap news agency quoted a government source as saying on Monday.
South Korean government officials were not immediately available for comment.
The latest launches, the first in about three months, come as Pyongyang has said it is ready to return to international talks on its nuclear weapons programme, though it has insisted it holds talks first with the United States.
It was not clear whether these were routine military exercises.
But they coincided with local media reports that the United States is planning to send its aircraft carrier USS George Washington to the South Korean port of Busan on Tuesday.
The reclusive North has hundreds of short-range range missiles, with the ability to strike the South Korean capital Seoul and its sprawling urban surroundings which are home to around 25 million people.
A nuclear test in May and a spate of missile tests around the same time triggered a tightening of sanctions against the North, whose desperate economic straits some analysts have said are partly behind its recent attempts to get on better terms with the outside world.
A U.N. resolution bans North Korea from launching ballistic missiles, but there are no international agreements that bar it from test-launching short-range missiles.