North Korea has test fired dozens of short-range rockets in the past 24 hours, the South's military says, in an apparent show of anger with Seoul.
Analysts say the launches are Pyongyang's way of protesting against joint military drills between the US and South Korea.
Some 16 rockets were fired into the sea early on Sunday, following the launch of 30 on Saturday.
Pyongyang claims its rocket tests are routine, self-defence exercises.
But the North has bitterly criticised the annual war drills by Washington and Seoul, labelling them invasion preparations.
The isolated state often makes a show of force at the same time as the drills.
But this year there have been an unusually high number of rockets launched.
Experts say some 70 missiles have been fired so far this month, including the 46 from this weekend.
The South Korean military says that the North appears to be firing Frog rockets, which are unguided Soviet-developed devices that Pyongyang has had in its armoury since the 1960s.
Both South Korea and the US have criticised the North's missile tests.
Earlier this month Seoul said that one such experiment took place in the same vicinity as a Chinese passenger plane.
Also in early March the US asked the UN Security Council to take "appropriate action" against North Korea's missile launches, which it said "clearly used ballistic missile technology".
Under UN resolutions, North Korea is required to abandon its ballistic missiles programmes.