South Korea's Defense Ministry says North Korea has test-fired seven ballistic missiles off its eastern coast.
The missiles are believed to have traveled about 400 kilometers each, falling into the Sea of Japan. With that range, the missiles would have the capability of striking most of South Korea and parts of Japan.
South Korean officials say the launches, which took place throughout the day Saturday, violate a recent United Nations resolution prohibiting North Korea from firing any ballistic missiles.
Japan called the launches a "serious act of provocation."
A spokesman for the U.S. State Department, Karl Duckworth said the North should "refrain from actions that aggravate tensions." He called the reported launches "not helpful."
The latest missile tests were taking place as the United States celebrates its July 4 Independence Day holiday.
Britain and France also condemned the missile tests.
North Korea has issued an advisory for boats to steer clear of its eastern waters until Thursday, indicating that more test launches may be coming.
Russia and China Saturday urged North Korea to return to negotiations on its nuclear program.
Following a meeting in Moscow between officials of the two countries, Russia issued a statement saying the six-party talks are the most effective way to resolve the nuclear issue. The talks also involve the United States, Japan and South Korea.
The missile tests add to the tensions on the Korean peninsula over North Korea's May 25 nuclear test and an April ballistic missile launch.
Separately, a South Korean news report Saturday said the North Korean cargo ship that changed course after being tracked by U.S. vessels appears to be carrying conventional small weapons, including Soviet-era rifles and missile launchers. The report by Yonhap news agency quoted an official who asked not to be named because the information had to do with intelligence. The Kang Nam 1 was believed to be on its way to Burma.
Newly imposed U.N. sanctions allow members to request a search of suspicious cargo to prevent Pyongyang from obtaining material needed for its nuclear and weapons programs.