The salvo, confirmed by the South Korean government, also appeared to be a slap at the United States as Washington moves to enforce U.N. sanctions as well as its own against the isolated regime for its May 25 nuclear test.

The launches, on July Fourth, were similar to a display that took place three years ago, also while Americans celebrated Independence Day during another period of tensions over Pyongyang's nuclear-weapons program.

The number of missiles was the same, though in 2006 North Korea also launched a long-range rocket that broke apart and fell into the ocean less than a minute after liftoff.

South Korea said that yesterday's missiles likely flew more than 250 miles, apparently landing in waters between the Korean peninsula and Japan.

South Korea and Japan both condemned the launches, with Tokyo calling them a "serious act of provocation." Britain and France issued similar statements.

Russia and China, both close to North Korea, expressed concern over an "escalation of tension in the region," the Russian Foreign Ministry said in a statement after a meeting in Moscow.

In Washington, the White House had no immediate comment. But two senior officials in President Obama's administration, speaking in advance of the launches, said that any reaction was likely to be muted to avoid giving attention to Pyongyang or antagonizing it. They spoke on condition of anonymity.

North Korea has engaged in a series of acts this year widely seen as provocative. It fired a long-range rocket that it said was a satellite in early April, and in late May it carried out its second underground nuclear test; the first was in late 2006.

In addition, North Korea convicted two American journalists last month and sentenced them to 12 years' hard labor for illegally entering the country. It is also holding a South Korean worker for allegedly denouncing its political system.

The secretive communist country is believed undergoing a political transition in which leader Kim Jong Il, 67, appears to be laying the groundwork to transfer power to one of his sons. Kim himself took over from his late father, the country's founder.

South Korean officials said that yesterday's launches came throughout the day and were part of military exercises. The North, which has warned ships to stay away from waters off the east coast through Friday, also fired what are believed to have been four short-range cruise missiles Thursday.

Speculation had been building for weeks that the launches were coming. The key question has been whether the North might fire an intercontinental ballistic missile, as it vowed to do in late April.

Despite a Japanese newspaper report last month that one might be launched toward Hawaii in early July, U.S. officials have noted no such preparations, which are complex, usually take days, and are often observable by spy satellites. Still, that hasn't stopped Washington from boosting missile defenses as a precaution.