Pyongyang launched seven missiles into waters off its east coast Saturday in a show of force that defied U.N. resolutions and drew international condemnation.
The missiles appear to have traveled about 250 miles (400 kilometers), meaning they could have reached almost any point in South Korea, an official at the South Korean Defense Ministry said on condition of anonymity, citing department policy.
The official said the exact details of the launches were still under investigation.
The launches on U.S. Independence Day appeared to be a poke at Washington as it moves to enforce U.N. as well as its own sanctions against the isolated regime for its May 25 nuclear test.
But Vice President Joe Biden indicated the U.S. would not be baited. He described the flurry of rockets as "attention-seeking behavior."
He added: "I don't want to give the attention."
North and South Korea, which fought a 1950-53 war, still face off across the world's most heavily fortified border. The United States, South Korea's key ally, has 28,500 troops stationed in the country as a deterrent.
The North's main Rodong Sinmun newspaper said in a commentary that "our revolutionary forces have grown up today as the strong army that can impose merciless punishment against those who offend us," crediting the country's "military first" policy.
The commentary was carried Sunday by the official Korean Central News Agency.
Last month, the North threatened a "thousand-fold" military retaliation against the U.S. and its allies if provoked.
North Korean leader Kim Jong Il has been devoting much of the country's scarce resources to his 1.2 million-member military under the policy.
South Korea's Yonhap news agency - citing a government source it did not identify - reported that five of the seven ballistic missiles landed in one area, indicating their accuracy has improved.
Yonhap said two of the seven missiles launched are believed to be variants of Rodong missiles while the rest are believed to be upgraded versions of Scud-C missiles.
The modified Scud-C versions have a range of up to 370 miles (600 kilometers), which could hit most of South Korea. Rodong missiles, meanwhile, have a range of up to 800 miles (1,300 kilometers), putting most parts of Japan within striking distance.
Yonhap said, however, that the range of the Rodong missiles launched Saturday had been reduced apparently to improve accuracy.
The agency also said the North is believed to have deployed 200 to 300 Scud missiles and 200 Rodong missiles, with many of the Scud missiles positioned near the border with South Korea and capable of reaching the Seoul metropolitan area within four to six minutes. Yonhap said some experts thought the North had 500 to 600 Scuds.
Another South Korean Defense Ministry official said no signs of additional missile launches had been detected, but more were possible given North Korea warned ships to stay away from the area through July 10. He also spoke on condition of anonymity citing department policy.
The North has engaged in a series of acts this year widely seen as provocative. It fired a long-range rocket it said was a satellite in early April, and in late May it carried out its second underground nuclear test following the first in late 2006.
Last month, it appeared to be flouting new U.N. sanctions again when a ship believed to be carrying illegal weapons set sail. Yonhap said Sunday, however, that the boat, which turned around a week ago, is now headed toward Korean waters.
Australia and Sweden were the latest countries to criticize the launches.
Australian Foreign Minister Stephen Smith, while calling the firings a "provocative act," also told the Nine Network in an interview Sunday that it is "important not to overreact."
Swedish Foreign Minister Carl Bildt, whose government assumed the rotating European Union presidency on July 1, called the launches "a conscious political provocation" and said the EU must support U.N. sanctions "in a robust way."
Koh Yu-hwan, a North Korea expert at Seoul's Dongguk University, predicted Pyongyang would now spend some time watching how the international community reacts to the launches.
"There will be a cooling off period for the time being," he said.