South Korean President Park Geun-Hye warned North Korea on Tuesday that its only "path to survival" lay in abandoning its nuclear and missile programmes.

In a speech to mark the third anniversary of the sinking of a South Korean naval vessel by what Seoul insists was a North Korean submarine, Park called on Pyongyang to "change course" at a time of elevated military tension on the Korean peninsula.

"For the North, the only path to survival lies in stopping provocations and threats, abandoning its nuclear weaponry and missiles, and becoming a responsible member of the international community," Park said.

The president delivered her speech at the national cemetery in the central city of Daejeon where the 46 sailors who died when the Cheonan corvette sunk are buried.

North Korea has always denied any involvement in the incident which precipitated a total freeze in South-North relations.

"Even now, North Korea is threatening our national security," Park said, citing Pyongyang's successful long-range rocket test in December and the third nuclear test it carried out last month.

Both events triggered UN sanctions that infuriated the North, which has spent the past month issuing increasingly dire threats about unleashing an "all-out war" backed by nuclear weapons.

Sabre-rattling and displays of brinkmanship are nothing new in the region, but there are concerns that the current situation is so volatile that one accidental step could escalate into serious confrontation and conflict.

Bruce Klingner, a Korea expert at the conservative Heritage Foundation in Washington, believes the "risk of miscalculation and escalation" is heightened by the presence of new leaders in both Koreas.

Kim Jong-Un, believed to be in his late 20s, succeeded his late father Kim Jong-Il as North Korea's supreme leader a little more than a year ago, while Park was only sworn in last month.

Park had campaigned on a pledge of greater engagement with North Korea, but February's nuclear test put any rapprochement on indefinite hold.

Kim, meanwhile, has spent the past few weeks touring frontline military units, monitoring live fire artillery drills and drone strikes and making inflammatory speeches about wiping out the enemy.

On the eve of the Cheonan sinking anniversary, Kim oversaw joint army and navy exercises to repel an amphibious landing along the eastern coast.

"He stressed the need to destroy the enemies in waters to the last man ... and send all of them to the bottom of the sea as they run wild like wolves threatened with fire," the official Korean Central News Agency reported.

In an open letter to troops published to mark the Cheonan anniversary, South Korea's hawkish defence minister, Kim Kwan-Jin, said there was a "high possibility" the North's threats might he translated into action.

He also reiterated that South Korea's response to any provocation would not only target the origin of the attack, "but also its supporting and commanding forces".

The South Korean and US militaries signed a new pact last week, providing for a joint military response even to low-level action by North Korea.

While existing agreements provide for US engagement in the event of a full-scale conflict, the new protocol addresses the response to a limited provocation such as a cross-border incursion.

It guarantees US support for any South Korean retaliation and allows Seoul to request any additional US military force it deems necessary.