This is dominating the Japanese news, for good reason. This is from the BBC.
BBC News - Artillery fire on Korean border
South Korea says it has returned fire after North Korea fired around 200 artillery shells onto one of its border islands, reportedly killing one marine.
The South's military was placed on its highest non-wartime alert after the shells landed on Yeonpyeong island.
North Korea has not yet commented on the incident, in which three marines and two civilians were also injured.
Correspondents say this is one of the most serious since the the Korean War ended without a peace treaty in 1953.
There have been occasional cross-border clashes since, but the latest incident comes at a time of rising regional tension.
North Korea's reclusive leader Kim Jong-il is believed to be ill and trying to engineer the succession of his youngest son. And on Saturday, North Korea showed off what it claimed was a new uranium enrichment facility - potentially giving it a second route to a nuclear weapon.
The move prompted the US special representative for North Korea, Stephen Bosworth, to rule out the resumption of six-party talks on resolving the nuclear issue.
South Korean presidential spokesman Kim Hee-jung also said it was investigating a possible link between the artillery attack and recent maritime exercises near the western sea border earlier on Tuesday.
'Illegal firing'
South Korean officials said artillery rounds began landing on Yeonpyeong island, near the disputed inter-Korean maritime border about 100km (60 miles) west of the Korean Peninsula.
You can see more information by clicking the link.