http://news.bbc.co.uk/2/hi/asia-pacific/4503531.stm
So uh, how long before the North Koreans do something crazy?
Japanese officials say they are checking reports that North Korea has test-fired a short-range missile into the Sea of Japan.
Japanese public broadcaster NHK said the missile had flown about 100km (62 miles) into the sea.
Japan has been monitoring North Korea after US warnings that it is close to testing its first nuclear warhead.
North Korea has already developed long-range missiles that reach Japan and has pulled out of nuclear talks.
In March the government said it was no longer observing a self-imposed moratorium on long-range missile testing which had been in place since 1999.
Uncompromising language
Japanese news agency Kyodo said Tokyo had been informed by the US military of the North Korean test, believed to have been carried out at 0800 (2300 GMT on Saturday).
The US has not commented on the reports.
At a time when every move by North Korea has been scrutinised by its neighbours, the test-firing of even a short-range missile is a cause for anxiety, says the BBC's Jonathan Head in Tokyo.
No-one outside the secretive communist state has any clear idea what its intentions are, our correspondent says. US officials fear North Korea is now preparing to test its first nuclear device after its announcement in February that it already possessed nuclear weapons and that it would not be coming back to the six-party negotiations over its nuclear programme.
On Thursday, a senior US intelligence official told senators in Washington that North Korea now had the capability to arm its missiles with nuclear warheads, although he was not sure how quickly it could do so.
A full nuclear test would run the risk of alienating China and South Korea that are vital for North Korea's ruined economy, says our Tokyo correspondent.
But analysts believe it may still feel it has to go ahead to prove to itself and to the world that it has mastered the technology to join the nuclear club, says our correspondent.
North Korea last launched a high-profile missile test in March 2003, to coincide with the inauguration of South Korean President Roh Moo-hyun.
These were two short-range land-to-ship missiles fired into the Sea of Japan.
It has not launched long-range missiles since 1998, when a Taepodong 1 missile flew over Japan.
So uh, how long before the North Koreans do something crazy?