South Korea holds rare military parade amid North's nuclear threat

South Korea kicked off its first large-scale military parade in a decade, with weapons ranging from ballistic missiles to attack helicopters due to roll through Seoul in a show of force as it takes a tougher stance against North Korea.

The parade marks the country's Armed Forces Day, normally a muted event relative to the massive events the North has staged under leader Kim Jong-un that include strategic weapons such as intercontinental ballistic missiles (ICBM).

In a speech at Seoul Air Base, President Yoon Suk Yeol warned Pyongyang against the use of nuclear weapons and pledged to ramp up support for the military and the defence industry.

"If North Korea uses nuclear weapons, its regime will be brought to an end by an overwhelming response from the ROK-U.S. alliance," Yoon said while addressing troops in the rain.

The full-day event will feature thousands of troops and South Korea's home-grown tanks and self-propelled artillery as well as attack aircraft and drones, joined by 300 of the 28,500 US soldiers based in the country, the Defence Ministry said.

The highlight will be a two-kilometre (1.24 mile) parade through Seoul's main commercial and business district to the bustling Gwanghwamun area which is the gate to a sprawling palace in the heart of Seoul.

South Korea last held a military street parade in 2013. The Armed Forces Day event and parade are being held before the actual day on Oct. 1, as it overlaps with a major national holiday this year.

The event comes as South Korean President Yoon Suk Yeol has taken a hawkish stance on North Korea, making displays of weapons and military drills a cornerstone of his strategy to counter the North's evolving nuclear and missile programs.

Yoon has promised a swift and overwhelming response against any aggression by Pyongyang, and has actively reinforced a military alliance with Washington and Tokyo since taking office last year.

Tuesday's parade kicked off at the airbase in Seongnam on the outskirts of Seoul, where Hyunmoo missiles, L-SAM missile interceptors, and reconnaissance drones were among military hardware on display.

A fly-past of F-35 jets and the country's first domestically developed fighter, the KF-21, was scrapped because of poor weather, the presidential office said.

Hyunmoo is one of South Korea's latest missiles, which analysts say is an integral part of Seoul's plans for striking the North during a conflict, while the L-SAM is designed to hit incoming missiles at altitudes of 50-60km.

The event will also feature a joint flyover by South Korean and US military aircraft to demonstrate an "upgraded" combined defence posture, the ministry said.

The parade comes a week after North Korean leader Kim Jong-un returned from a trip to Russia, during which he and Russian President Vladimir Putin agreed to boost military cooperation.

Yoon has said that if Russia helped North Korea enhance its weapons programme in return for assistance for its war in Ukraine, it would be "a direct provocation".