Seoul believes North Korea torpedoed navy ship

South Korea's military believes that a North Korean submarine launched a torpedo attack that sank a South Korean warship last month near their disputed sea border, Yonhap news agency said yesterday.

The assessment was reported to the office of President Lee Myung-Bak and the defence ministry immediately after the ship sank last month, an unnamed senior military source told Yonhap.

"It's our military intelligence's assessment that North Korean submarines attacked the ship with a heavy torpedo," the source said, adding that the subs were armed with torpedoes with 200-kilogram warheads.

"Since February last year, North Korea has strengthened training that showed the possibility of it launching a guerrilla warfare-style provocation, rather than a skirmish."

The South's military intelligence command had also alerted the navy ahead of the March 26 sinking of the Cheonan that North Korea was preparing an attack, Yonhap said.

The South's defence ministry refused to comment on the report.

Seoul has so far refrained from directly accusing Pyongyang and said only that an "external explosion" was the most likely cause of the disaster which cost the lives of 46 sailors.

Pyongyang has denied it was responsible.

South Korean Defence Minister Kim Tae-Young has already raised the possibility that a mine or torpedo may have sunk the ship, following deadly naval clashes in 1999 and 2002 and a November firefight.

The November incident left a North Korean patrol boat in flames and local media reports said one North Korean sailor was killed and three wounded.

The North has vowed "merciless" military action to protect what it sees as its Yellow Sea border.

South Korea's Chosun Ilbo newspaper meanwhile quoted defectors as saying that North Korea had formed suicide attack squads known as "human torpedoes" in its navy.

It said the North's navy operates a brigade of suicide attack squads, which have many mini-submarines capable of carrying torpedoes or floating mines.

High-ranking defector Hwang Jang-Yop told the newspaper yesterday it was "obvious" the communist regime's leader Kim Jong-Il was behind the sinking.

"It is obvious Kim did it, and it is a widely known fact that he has been preparing for this kind of (terrorism)," he said.

The regime has lived on oppression and terrorism, Mr Hwang said, adding Mr Kim wanted to cause chaos on the Korean peninsula.