N Korea's missile launches 'not helpful': US

''We're waiting until we have all the facts about the violation,'' State Department press officer Karl Duckworth said.

Both South Korea and Japan have condemned the firings as violations of UN sanctions, the most recent of which was passed last month in reaction to Pyongyang's test explosion of a nuclear bomb.

The Pentagon, which in the past has been the US agency which confirms North Korea's illicit missile launches, said it was not in a position to confirm North Korea's firing of seven missiles early on Saturday.

Duckworth said the US was "aware of a possible missile launch by North Korea" and was closely monitoring Pyongyang's activities and intentions.

"This type of North Korean behaviour is not helpful. What North Korea needs to do is fulfill international obligations and commitments," Duckworth said, reading from a statement.

The South Korean defence ministry said North Korea fired seven missiles within a ten-hour span. The launches, from the country's eastern coast, came on top of four test firings Thursday that had already left the region on edge.

The latest missiles, with a range of 400 to 500 km, were fired over the Sea of Japan, the ministry said.

There was some suspicion that North Korea was taking advantage of the US July 4 Independence Day holiday to show off its strength, as it has in the past.

South Korea's Foreign Ministry called the missile firings a "provocative act that clearly violates UN Security Council resolutions 1695, 1718, and 1874 that bar North Korea's every activity related to ballistic missiles".

Japan also condemned the rocket launches. Chief Cabinet Secretary Takeo Kawamura said North Korea's action was "a serious act of provocation against the security of neighbouring countries, including Japan, and is against the resolution of the UN Security Council".