Fox:

The South Korean navy reportedly shot at unidentified ships near North Korea and is investigating whether a sinking ship in its navy was hit with a torpedo near the maritime border with the communist North.

AP:

Earlier Friday, North Korea’s military threatened “unpredictable strikes,” including a nuclear attack, in anger over a report that South Korea and the U.S. were preparing for possible instability in the totalitarian country.

After the ship began sinking, President Lee Myung-bak convened an emergency meeting of security-related ministers, Yonhap said, citing presidential spokeswoman Kim Eun-hye. She said it wasn’t clear yet whether North Korea was involved in the ship’s demise.