North Korea test-fired short-range missiles today in what analysts saw as a show of the state's anger at Washington and the new conservative government in Seoul.
A South Korean presidential spokesman said the North had fired short-range missiles as a part of a military exercise. News reports said the three were ship-to-ship missiles launched into the sea off the west coast.
The launch comes a day after the North expelled South Korean officials from a joint industrial complex north of the border, after Seoul told its North Korea to clean up its human rights and stop dragging its feet in nuclear disarmament talks.
New South Korean President Lee Myung-bak has said he wants to end the free ride given to North Korea under 10 years of left-leaning presidents who gave billions in aid while asking for little in return, seeing it as the price to pay for stability.
Mr Lee's government has said it is ready to invest heavily, provided the North meets conditions such as scrapping its nuclear arms programme or returning the more than 1,000 South Koreans it kidnapped or kept in the country after the 1950-53 Korean War.
North Korea has more than 1,000 missiles, at least 800 of them ballistic, that can hit all of South Korea and most parts of Japan, experts have said. Its launches are often timed to coincide with periods of political tension.