South Korea staged its largest military display for a decade on Tuesday, as President Park Geun-Hye warned of the "very grave" threat posed by North Korea’s nuclear weapons program.

South Korea staged its largest military display for a decade on Tuesday, as President Park Geun-Hye warned of the "very grave" threat posed by North Korea's nuclear weapons program.

Some 11,000 troops and 120 aircraft took part in the event at an air base south of Seoul, which showed off the military's most advanced weaponry, including a cruise missile capable of surgical strikes on the North Korean leadership.

The guest of honor was US Defense Secretary Chuck Hagel -- on a visit tounderscore US commitment to its military alliance with South Korea where 28,500 US troops are currently stationed.

"The situation on the Korean peninsula ... is very grave," Park warned in her speech at the event marking the 65th anniversary of the founding of South Korea's armed forces.

"North Korea adamantly continues to develop and upgrade its nuclear weapons," Park said, adding that the South had no option but to boost its military deterrent in response.

She specifically cited the development of sophisticated missile interceptor systems capable of neutralizing a North Korean strike.

"I believe that the true purpose of the military lies not in fighting a war but preventing one," she said.

Among the hardware on display was the Hyeonmu 3, an indigenously developed cruise missile that was first deployed on naval destroyers in November last year.

South Korea has cited the growing nuclear threat from Pyongyang to back its request for extending US command of combined US and South Korean forces in the event of war with the North.

South Korea is scheduled to take over wartime operational command in 2015, but defense policymakers now say they need more time to prepare for the transition.

Tuesday's display at the air base was to be repeated later in the day with a mass military parade in downtown Seoul -- the largest since 2003.