Flowers are laid on the site of a deadly stampede in Seoul's Itaewon district on Sunday. (Yonhap)

South Korea has officially entered a weeklong national mourning period for the victims of Saturday night’s human stampede in Itaewon, which was recorded as one of the worst peacetime disasters in the country with over 150 casualties.

“Following the president’s directive, the government has decided to observe a national mourning period until midnight of Nov. 5, during which the nation will mourn the perished,” Prime Minister Han Duck-soo told a media briefing.

A joint altar for the victims will be set up at a location in Seoul that has yet to be decided, he added.

During the period, all government offices and overseas missions will lower their flags to half-mast and cancel or postpone nonessential public events. Civil servants and employees of public institutions will wear ribbons to express their condolences, officials explained.

At least 153 people were killed and many injured, particularly at a narrow and sloped street in Itaewon, as over 100,000 partygoers flocked to the capital’s most popular party district for the first Halloween festivities since the lifting of social distancing rules.

Many of the victims were young partygoers in their 20s, and they include at least 20 foreigners.

The incident sent a shock wave through South Korea, which had welcomed the return of festivals, large concerts and gatherings only recently.

With many people expressing grief and sorrow and criticizing the apparent lack of crowd control, Halloween-themed festivals and other events expected to draw large crowds were canceled from Jeju Island to Busan and Seoul.

Busan City announced the cancellation of a K-pop concert, slated to be held at Busan Asiad Main Stadium on Sunday evening as part of the Busan One Asia Festival. Over 40,000 were expected to attend.