South Korea expressed its condolences to North Korea over a recent deadly collapse of an apartment building in Pyongyang, an official said Tuesday, a rare goodwill gesture after recent harsh verbal tit-for-tat between the archrivals.

"We convey our deep condolences over the loss of many lives in the accident," South Korea's Red Cross said in a message sent to its North Korean counterpart earlier in the day through a dialogue channel at Panmunjom, a neutral village on the inter-Korean border.

The move came two days after North Korea reported that an apartment building collapsed in the Phyongchon District in Pyongyang in what state media called "a serious accident."

North Korea has said improper construction and irresponsible supervision of the high-rise construction are to blame for the May 13 disaster, though it did not elaborate on the death toll.

Senior North Korean officials have offered a rare public apology to a group of North Korean people in what could be the first public apology over an accident in the communist country.

South Korea suspects that a "considerable" number of people were killed in the accident, noting about 92 households may have been living in the 23-story building.

The International Federation of Red Cross and Red Crescent Societies said it has not received any request for help from North Korea over the apartment collapse, according to the Washington-based Radio Free Asia.

In April, North Korea expressed its condolences to South Korea over the sinking of a South Korean ferry that left more than 300 people, mostly high school students, dead or missing.

The North's rare conciliatory gesture came amid its diatribe and threats against South Korea over alleged slander and comments critical of the North. The North has called the unmarried female South Korean leader "an old prostitute."

On Monday, the North also called the ferry disaster "a deliberate act of murder and a massacre" in the latest attack on South Korea.

The South's condolences are the first of their kind since 2006 when a devastating flood in North Korea left hundreds of people dead or missing.

Inter-Korean relations are currently at one of their lowest points in many years. In late March, both sides exchanged hundreds of live artillery rounds across their yellow sea border in their latest military tit-for-tat. No one was hurt. (Yonhap)