South Korea is staging its largest military parade in a decade, as President Park Geun-hye warns of a “very grave” threat from North Korea.
Cruise missiles and torpedoes were amongst the weapons displayed in the Armed Forces Day parade, reports said.
US Defense Secretary Chuck Hagel and General Martin Dempsey also attended the event marking the 65th anniversary of South Korea’s armed forces.
They are currently in South Korea for security talks.
“The situation on the Korean peninsula… is very grave,” President Park Geun-hye said in a speech at the event.
“We have to build strong deterrence against North Korea until the North abandons its nuclear programme and makes the right choice for the people of North Korea and peace on the Korean Peninsula,” she added.
South Korea has displayed advanced weaponry during the parade, including the Hyunmoo 3 cruise missile, which Seoul says is capable of precision strikes on North Korean targets.
Around 11,000 soldiers and 120 aircraft were mobilized for the event.
Chuck Hagel, who is visiting South Korea for the first time since becoming defense secretary, has reiterated the US’s commitment to its military partnership with the South.
He and President Park Geun-hye are expected to discuss the eventual transfer of operational military control to Seoul.
Tensions between the two Koreas rose earlier this year, after North Korea’s third nuclear test in February.
Angered by expanded UN sanctions and annual US-South Korea military drills, Pyongyang threatened attacks on Japanese, South Korean and US military targets in the region.
Earlier this month, satellite imagery also suggested that North Korea had restarted a reactor at its Yongbyon nuclear facility, and tested a long-range rocket engine, a US think tank said.