SEOUL (Reuters) -- North Korea has fired seven ballistic missiles, South Korea's Defense Ministry said, in an act of defiance toward the United States that further stoked regional tensions already high due to its nuclear test in May.
South Korea's Yonhap news agency said the missiles test-fired were "Scud-type," marking an escalation of recent saber-rattling by the reclusive North, which has fired several nonballistic, short-range missile since the May 25 nuclear test.
North Korea is barred by United Nations resolutions from firing ballistic missile such as the Scud. A South Korean Defense Ministry official said more launches could come soon.
It was the biggest barrage of ballistic missiles the North has fired since it launched seven missiles in 2006 around the U.S. July 4 Independence Day holiday, including its longest-range Taepodong-2.
The launches came as the United States has cracked down on firms suspected of helping the North in its trade in arms and missiles, which were subject to UN sanctions imposed after the nuclear test and are a vital source of foreign currency for the cash-short state.
An anonymous South Korean official quoted by Yonhap said the launch may have been intended to send a message to Washington, the North's main foe who for years has been trying to press Pyongyang to end its atomic ambitions and rein in missiles that threaten U.S. allies South Korea and Japan.
"Today's missiles seem to have political purposes in that they were fired a day ahead of the U.S. Independence Day," the agency quoted the official as saying.
Peter Beck, an expert on Korean affairs at the American University in Washington, said: "If the North Koreans are trying to get our attention, it is difficult to see what they are actually trying to accomplish."
South Korea's Defence Ministry confirmed the North fired seven missiles off its east coast from morning to late afternoon that flew about 400 kilometers and splashed into the sea.
"It is a provocative act that clearly violates UN Security Council resolutions," Yonhap quoted a statement from South Korea's Foreign Ministry as saying.
Japan's Foreign Ministry said in a statement the country "strongly protests and regrets today's missile launches by North Korea as they are a serious act of provocation against the security of neighboring countries, including Japan."
North Korea is thought to have more than 600 Scud-type missiles that include the Hwasong-5, with a range of about 300 kilometers and the Hwasong-6, with a range of about 500 kilometers.
It also has more than 300 mid-range Rodong missiles that can hit all of South Korea and most of Japan. Weapons experts said the North does not have the ability to miniaturize a nuclear weapon to mount as a warhead on a missile.
North Korea fired four short-range, nonballistic missiles into the sea off its east coast on July 2.
The U.S. envoy who coordinates sanctions against the North was in China earlier this week to enlist Beijing's help in getting tougher with North Korea.
China is the North's biggest benefactor and trade partner whose help would be essential for an effective sanctions regime, analysts said.
Daniel Pinkston, with the International Crisis Group in Seoul, said the test helps the North's military in its missile capabilities and could also be linked to the sanctions.
"The sanctions raised the cost of products such as missile systems. Buyers, who are taking increased risks, want to be assured about the quality and reliability of the product," said Pinkston.
North Korea fired a rocket it said put a satellite into space in April. U.S., South Korean and other officials said the launch was a disguised test of the long-range Taepodong-2 missile, which could hit U.S. territory, and nothing was put into orbit.
The North has also threatened to fire another Taepodong-2, but there has been no indication it has started preparations of placing a rocket on a launch pad and fueling it, a process that takes about four days and can be seen by U.S. spy satellites, South Korean officials have said.
The North has raised tension in recent months by saying it has started a program to enrich uranium, which could give it a second path to a nuclear bomb, threatening to attack the South, and extracting plutonium at its aging Yongbyon nuclear plant.
Analysts said the moves may be aimed at securing internal support for leader Kim Jong Il, 67 and thought to have suffered a stroke a year ago, as he prepares the ground for his youngest son to succeed him at the head of Asia's only communist dynasty.