``Nine bodies were found inside the sub,'' the defence ministry said in a statement. Four had bullet wounds to the head while five other bodies were riddled with bullets.

``It seems that there might have occurred a brawl over what they should do and the first group of four people might have killed the second group of five before committing suicide by shooting themselves in the head,'' it said.

The bodies were found in the vessel's cabin by navy commandos who carried out an overnight search after entering the submarine and checking the inside for fear the hatches might be booby-trapped.

Two AK-47 rifles, a rocket launcher, two machine guns, two Czech-made handguns and two grenades were found, plus US-made diving equipment and two bottles of South Korean-made soft drink.

``Consideringtheir clothes and weapons and other materials, it is certain that the submarine was engaged in an infiltration mission by the North's special agents,'' the ministry said.

It urged the North to apologize for the ``serious act of military provocation'' and take steps to prevent a recurrence.

It also called for another round of high-level military talks between the US-led United Nations Command (UNC) and North Korea to discuss the intrusion.

The UNC lodged a protest with the North over the submarine intrusion at the military talks which resumed Tuesday for the first time in seven years.

Television showed bodies, with the legs clad in black trousers and dark sneakers sticking out from blankets wrapped around them, being pulled through the submarine hatch and carried away by South Korean navy troopers wearing medical masks.

The vessel was captured Monday in South Korean waters after becoming entangled in fishing nets.

South Korean authorities had hoped to interrogate the crew about theirmission.

North Korea said Tuesday that a ``small submarine'' was ``wrecked'' during a training exercise off Kosang in the East Sea of Korea (Sea of Japan), and that a search was under way. The mini-sub, which sunk in 30-metre deep water 1.8 kilometers (1.125 miles) off Tonghae while being towed into Port, was re-floated by divers using airbags and towed to the pier.