South Korean and US troops Friday held their biggest single-day joint live-fire exercise to test responses to any North Korean attack, amid high tensions on the peninsula.

The drill at Pocheon near the North Korean border involved some 2,000 troops along with jet fighters, tanks, Apache attack helicopters, A-10 "tank-killer" aircraft, missiles and multiple rocket launchers, the defence ministry said.

The two allies are also due Saturday to launch a major three-day naval exercise in the tense Yellow Sea, ahead of the 62nd anniversary Monday of the outbreak of the Korean War.

On Thursday the US, South Korea and Japan began a separate two-day drill off the southern South Korean island of Jeju, involving destroyers, supply ships and helicopters. North Korea denounced it as a "reckless provocation".

Tensions are high after the North's failed rocket launch in April, seen by the US and its allies as an attempted ballistic missile test.

Pyongyang has also threatened attacks on the South's government and conservative media for perceived insults to its regime.

The first stage of the drill at Pocheon, 35 kilometres (22 miles) from the border, aimed to practise a response to a shooting and shelling attacks on South Korean border outposts.

The second stage assumed an all-out attack by North Korean forces.

Apache helicopters and A-10 aircraft were to strafe assumed enemy positions and two South Korean multiple rocket launchers would join in the attack.

The exercise was to end with a cargo plane dropping ammunition and food to friendly forces and 60 commandos parachuting onto enemy positions.

The Yellow Sea naval exercise will involve 10 South Korean warships plus the USS George Washington aircraft carrier and striker group, 8,000 personnel and hundreds of combat aircraft, the South Korean Joint Chiefs of Staff said.

The joint naval drill is conducted every year, alternatively in the Sea of Japan (East Sea) and the Yellow Sea.

"Throughout the joint military exercises, South Korean and US forces will test their ability for joint operations and enhance combat-readiness," Navy Brigadier General Park Seong-Bae said in a statement.

"We will immediately retaliate against any attacks from North Korea and finish the enemy off on the spot," he said.