SEOUL (Reuters) - North Korea published comments on Friday attacking South Korean President Park Geun-hye, descending to unprecedented levels of personal insult by describing her as a "repulsive wench" who had failed to marry or bear children.

The brutal denunciation, going far beyond previous criticism in the reclusive authoritarian state's media, was certain to deepen animosity amid growing tensions on the world's most militarised border.

The KCNA news agency carried what it said were comments by a private citizen criticising Park's offer last week to help the impoverished North's women and children as "foul-smelling vituperation uttered by human scum.

"Park Geun-hye is but an unseemly wench who has never had a chance to marry or bear a child," the citizen, Kim Un Kyong, was quoted as saying by KCNA.

Park, the citizen said, had no right to talk about the children of North Korea.

"A repulsive wench such as Park Geun-hye is an incoherent existence who has long given up trying to be a woman of Korea and who makes a mockery of sacred motherhood, mad with the pursuit of national confrontation."

North Korea tightly controls the content of its media, frequently dominated by articles lionising past and present leaders. Dispatches often quote people said to be private citizens or obscure foreign groups to attack the South and the United States.

North Korea has steadily raised the level of insult against Park in recent weeks, after accusing the South of breaking an agreement to work to improve ties by stopping statements slandering of each others' leaders.

In late March, a North Korean agency that handles ties with the South criticised Park's comments at a summit with U.S. President Barack Obama and Japanese Prime Minister Shinzo Abe calling on Pyongyang to abandon its nuclear programme.

North Korea accused the South of "gangster-like" behaviour after the South returned a fishing boat that had strayed into its waters last week near a tense disputed naval border.

It then fired more than 500 artillery rounds off its shore on Monday, landing more than 100 in South Korea's waters. The South responded by firing back 300 rounds into the North's waters.

(Reporting by Jack Kim; Editing by Ron Popeski)