An apartment building under construction in the North Korean capital of Pyongyang has collapsed, sparking fears hundreds of people may have been killed.
North Korean officials have offered a rare public apology for the collapse, which a South Korean official said was believed to have caused considerable casualties.
The word of the collapse in the secretive nation's capital was reported on Sunday morning (local time) by the North's official Korean Central News Agency, which gave no death toll but said that the accident was "serious" and upset North Korea's leader, Kim Jong Un.
The report said it occurred in the capital's Phyongchon district on Tuesday "as the construction of an apartment house was not done properly and officials supervised and controlled it in an irresponsible manner."
In Seoul, a South Korean government official speaking on condition of anonymity because of the sensitivity of the information said the 23-storey apartment building that collapsed was presumed to have housed 92 families.
That could mean the casualties could be in the hundreds because a typical North Korean family has four members. However, it was not clear whether all the residents were inside at the time of the collapse, or that four people lived in each apartment.
It is not unusual for people to start living in apartments before the construction is complete.
The official said he did not have any figure for the actual death toll.
According to the KCNA report, the rescue operation ended on Saturday and officials apologised to bereaved families and district residents.
On the streets of Pyongyang on Sunday, residents expressed outrage over the incident.
"This accident happened because they broke the rules and methods of construction," resident Pak Chol told The Associated Press. "After this accident, we must make sure that this kind of terrible accident never happens again, by sticking to the proper method of building."
Another resident, Hong Nam Hyok, said that "everyone in Pyongyang is now sharing the sorrow of the victims and the bereaved families."
The KCNA report cited one official as saying Kim Jong Un "sat up all night, feeling painful after being told about the accident."
North Korea's highly controlled state media rarely report news that might be considered negative, and an admission of fault by the government is unusual.
The country regularly blames South Korea for starting the 1950-53 Korean War, although outside historians say that the North attacked first.
North Korea also denies responsibility for an attack on a South Korean warship that killed 46 people in 2010, despite a South Korean-led international investigation that blamed a Pyongyang torpedo.
Sometimes, however, the country owns up to failures. Many were surprised when the North admitted in 2012 that a high-profile rocket launch fizzled soon after takeoff - an acknowledgement that followed Pyongyang's claiming of success for other such launches that foreign governments said had been failures.
The building collapse came at a time when the South Korean government has received near daily criticism from its citizens as well as regular bashing by North Korean media for its handling of last month's ferry sinking that left more than 300 people dead or missing.