The two cruise missiles carrying mock nuclear warheads were fired towards the West Sea of the peninsula and flew 1,500km at a preset altitude of 150m.

This will be their first combined drills since 2021.

The US Indo-Pacific Command says the latest launch posed no threat to the US or its allies but Pyongyang's weapons of mass destruction and ballistic missile programs have a destabilising effect on the region.

At the heart of the drills was addressing the vast distances that the US, Britain and Australia would contend with when operating across the Pacific, and improving inter-operability of the three countries' air forces.

The US and South Korea began one of their largest combined military air drills, with hundreds of warplanes from both sides staging mock attacks 24 hours a day for the better part of a week.

The North fired some 100 shells into the sea off its west coast around 10pm and shot a further 150 rounds off its east coast, the South's Joint Chiefs of Staff says.

The missile launch was the sixth in 12 days and the first since North Korea fired a missile over Japan, which prompted joint South Korean and US missile drills during which one weapon crashed and burned.

The drills will be held in international waters off the Korean peninsula's east coast, after North Korea fired two ballistic missiles and US Vice President Kamala Harris visited Seoul.

China staged war games last month, angered by what it saw as a strong show of US support for the island Beijing claims as its own territory.

Taiwanese forces have closely monitored China's moves, scrambling fighter jets and deploying warships to keep guard against the Chinese navy.

The US has no formal diplomatic ties with Taiwan but is bound by law to provide the democratically governed island with the means to defend itself.

Drills have included launches of ballistic missiles, some of which flew over the island's capital of Taipei, and simulated sea and air attacks in surrounding skies and waters.