North Korea Saturday condemned a recent visit by the South's President Lee Myung-Bak to an island close to their disputed border and reiterated that it only recognises a demarcation line drawn by Pyongyang.

A National Defence Commission spokesman said Lee's trip Thursday to Yeonpyeong island, shelled by the North in 2010, intended to raise tensions and rally support for the conservative ruling party ahead of December elections.

The spokesman also reiterated Pyongyang's opposition to the Northern Limit Line (NLL) -- a frontier drawn by the US-led United Nations Command at the end of the 1950-53 Korean War to prevent any accidental clashes between the two.

"This (visit) is a revelation of his (Lee's) foolish attempt to disturb the nation's peace and stability, escalate confrontation and provoke a war by preserving the NLL, the root cause of confrontation and clash," the spokesman was quoted as saying by the official Korean Central News Agency (KCNA)

"NLL is an illegal bogus line drawn by the U.S. imperialist aggressor forces unilaterally and in a brigandish manner.

"Only maritime military demarcation line set by the DPRK (North Korea), not NLL, will remain in the West Sea till the country is reunified," he added.

During his visit President Lee urged soldiers on Yeonpyeong to defend the sea border at any cost. It came more than two years after Seoul accused Pyongyang of torpedoing one of its warships there, causing the loss of 46 lives.

The North denied involvement in the March 2010 incident but went on to shell a border island that left four South Koreans dead in November of the same year.

The North's spokesman added that Lee's visit was "a cynical ploy" ahead of the South's presidential election in December to "create conditions favorable for the conservative ruling party's stay in power".

Lee is unable to run for a second presidential term in the election because the country's constitution limits presidents to one five-year term.

Last month, the South urged the North to stop trying to influence the election, warning of a strong military response against any provocative act.