A Chinese military submarine has run into trouble in the South China Sea.
The incident was first reported by Japanese media, which said that a Chinese naval submarine caught fire at sea during an exercise and was being monitored by the U.S. and Japanese governments as it was being towed toward southern China.
Japan's defense agency chief, Yoshinori Ono, told reporters Tuesday that he wants to withhold releasing information about the incident, which he calls a sensitive matter.
Mr. Ono confirms he has been briefed about the accident and that the submarine, spotted between Taiwan and Hainan island, does not pose a threat to Japan's security.
Japanese media say the fire apparently damaged the diesel-powered vessel's propulsion system.
In Beijing on Tuesday, Chinese foreign ministry spokesman Kong Quan would not confirm that the sub had been damaged.
Mr. Kong says that he has confirmed with relevant government agencies that the submarine was carrying out a military mission.
The vessel is believed to be of the so-called Ming class hunter-killers submarines, which are 76-meters long and normally carry a crew of about 60.
In April 2003, China suffered one of its worst known military disasters when 70 sailors aboard a submarine died in a mysterious accident in the Yellow Sea.
This latest incident is in waters considered strategically important. Several countries have conflicting territorial claims in the area, and China conducts frequent military drills there.
Defense analysts here say in the event of a clash between China and Taiwan, China would likely set up a blockade in the area to attempt to halt American aircraft carriers from coming to Taiwan's aid.