S. Korean president vows to make Pyongyang 'pay the price' for attack

South Korean President Lee Myung-Bak on Monday vowed to make North Korea "pay the price" for its "inhumane" artillery attack on a frontline island that killed four people and sparked global outrage.

Lee has come under pressure to take a tougher line against Pyongyang after his military's counter-fire following North Korea's deadly artillery strike on a border island last week was seen as feeble.

"I can't help expressing anger at the North Korean regime's brutality," he said in a nationally televised address.

"Now our people know that any more tolerance and patience will only fan bigger provocations," he said of the regime that has previously tested nuclear bombs and is blamed for sinking a South Korean warship, killing 46 people.

A day after China, North Korea's last major ally, called for emergency talks with Pyongyang, Lee said that it is "difficult to expect North Korea to abandon military brinkmanship and nuclear weapons".

His speech comes as the US and South Korean navies stage a potent show of force against North Korea, carrying out a four-day joint naval exercise led by the nuclear-powered aircraft carrier USS George Washington.