South Korea will hold a major military exercise near the disputed Yellow Sea border with North Korea later this month when Seoul hosts a global forum, officials said Wednesday.

The drill involving warships, jet fighters and Marine units will be staged as part of events to mark the second anniversary of the sinking of a corvette, the defence ministry said.

"It may come around March 26, but details have yet to be fixed," a ministry official told AFP on condition of anonymity.

Seoul accused its neighbour of torpedoing the ship on March 26, 2010, with the loss of 46 lives. The North denied responsibility for the sinking but shelled a South Korean border island eight months later, killing four people.

The exercise will show "our firm readiness to punish" any provocations by the North, a senior ministry official told reporters.

He said soldiers would hold drills or rallies separately at their barracks on March 26, when dozens of national leaders including US President Barack Obama gather for the Nuclear Security Summit in the capital.

The summit will focus on ways to safeguard atomic material worldwide and prevent acts of nuclear terrorism. The North has blasted it as an "unsavoury burlesque" intended to justify an atomic attack by South Korea and its US ally.

Pyongyang's new leaders have agreed a nuclear deal with the United States but have taken a consistently hostile tone with the South's conservative government and its President, Lee Myung-Bak.

The North has several times threatened to launch a "sacred" war against the South over what it sees as insults to new leader Kim Jong-Un and his late father Kim Il-Sung.

A South Korean defence ministry spokesman confirmed media reports that a military unit based at Incheon, west of Seoul, had posted photos of the two Kims inside a barracks, with messages reading "Let's beat Kim Jong-Il to death! Let's strike Kim Jong-Un to death!"

The spokesman declined to say whether the photos or messages were still on display, saying such matters were the responsibility of individual units.

The South's Yonhap news agency said Wednesday that about 130 North Korean officials visited the tense land frontier last week as Pyongyang intensified its threats.

The North's Defence Minister Kim Yong-Chun and military chief Ri Yong-Ho toured the border truce village of Panmunjom on March 4, Yonhap quoted an unidentified South Korean military official as saying.

The official said mid-level officials have since travelled to the village and vehicles carrying oil, food and other supplies were sighted in the area.

US and South Korean military officials had no comment on the report.

Kim Jong-Un on March 3 made a surprise inspection visit to the village, which straddles the borderline, and placed troops there on alert. He has made a series of trips to frontline military units since his father's death on December 17.