South Korea voiced regret Monday at North Korea's rejection of its offers for talks at various levels as both countries prepare to mark the 70th anniversary of the Korean peninsula's liberation from Japanese colonial rule.

Last week, Seoul's parliamentary speaker Chung Ui-Hwa had used the August 15 anniversary as a peg to offer talks with his North Korean counterpart, Kim Yong-Nam.

On the same day, the South's defense ministry asked Pyongyang to attend September's Seoul Defense Dialogue, a security forum to which some 30 nations including the US and China have been invited.

But Pyongyang rejected both proposals over the weekend, describing them as "shameless" attempts to conceal Seoul's hostile policy towards the North.

"We find it very regrettable that the North rejected the offers ... and disparaged our efforts to have dialogue," Seoul's unification ministry spokesman Jeong Joon-Hee said.

"We hope that the North will respond to our offers for talks and take the path for ...progress of inter-Korea ties," Jeong told reporters.

The North's Committee for Peaceful Reunification of Korea, which handles cross-border ties, said South Korea's joint military exercises with US forces earlier this year revealed the "hypocrisy" of its peace overtures.

The North has habitually slammed the annual joint military drills, calling them rehearsals for war.

Cross-border tensions have flared at regular intervals this year, with the North conducting a series of ballistic missile tests in anger at the military exercises.

And Pyongyang was infuriated by the opening last month of a new UN office in Seoul to monitor the North's widely-criticised human rights record.

This year's 70th anniversary of liberation from japanese rule had been touted as an opportunity for the two Koreas, who remain technically at war, to make some gesture of reconciliation.

But plans for some sort of joint celebration have failed to materialise.