US and South Korean warships and aircraft practised anti-submarine manoeuvres off the Korean peninsula on Monday that the military hoped would serve as a warning to Pyongyang that aggression in the region would not be tolerated.

Meanwhile in the North Korean capital Pyongyang, a senior military official, Kim Young-Chun, threatened to mobilise his country's military and its "nuclear deterrence" to wipe out any military aggressors.

The nuclear-powered supercarrier USS George Washington was among the vessels taking part in Monday's exercises, which come in the wake of an international investigation which blamed the North for the sinking of a South Korean warship, the Cheonan, killing 46 sailors.

The four-day "Invincible Spirit" exercises, involving 20 ships, 200 aircraft and about 8,000 US and South Korean sailors, are being held in the waters off Korea's east coast, and have brought threats of retaliation from North Korea, which denies responsibility for the attack on the Cheonan.

But US officials say that the manoeuvres, held well away from North Korea's border, are not intended to provoke a response, although they do want to send Pyongyang a message that further aggression in the region will not be tolerated and that the alliance between the US and South Korea remains strong.

The anti-submarine phase of the training, which also involves anti-ship and anti-aircraft operations, is particularly important because an international investigation found that the 1,200-ton corvette Cheonan was sunk by a torpedo launched from a North Korean submarine that somehow penetrated South Korea's defences.