"From the view of the peaceful use of space and international security, we naturally have concerns about it," Chief Cabinet Secretary Yasuhisa Shiozaki, the government spokesman, told a news conference.

He said Japan was asking the Chinese foreign ministry to explain details about the test, in which the US confirmed a magazine report that a ballistic missile successfully destroyed an old Chinese weather satellite.

The United States and Australia have also expressed concern about the test, which US spy agencies said took place on January 11 at more than 500 miles (800 kilometers) above Earth.

Japan has recently been improving relations with China, which were badly strained under former prime minister Junichiro Koizumi who repeatedly visited a controversial shrine to Japanese war dead.

But Japan has repeatedly expressed unease about China's rapidly growing military spending and urged the European Union not to lift its ban on arms exports to Beijing.

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