The Prince and Princess of Wales have sent their “love and prayers” to those grieving loved ones after 151 people were killed in a crowd surge during Halloween festivities in Seoul, South Korea.

The victims, mostly aged in their teens and 20s, were crushed when a huge Halloween party crowd surged into a narrow alley in the Itaewon nightlife district on Saturday night.

A message on the Kensington Palace Twitter account said: “Catherine and I send all our love and prayers to the parents, families and loved ones of those tragically lost in Seoul yesterday evening. W & C.”

William’s message came after Prime Minister Rishi Sunak described the deaths as “horrific news”, adding in a statement on Saturday: “All our thoughts are with those currently responding and all South Koreans at this very distressing time.”

Foreign Secretary James Cleverly said he was “saddened by the tragic situation”, while Labour leader Sir Keir Starmer said it was “horrendous news”.

Tens of thousands of people were believed to have gathered in Itaewon for Halloween festivities.

Choi Seong-beom, chief of Seoul’s Yongsan fire department, whose jurisdiction includes Itaewon, said 19 foreign nationals were among those killed, the Associated Press news agency reported.

The Chinese state news agency Xinhua said at least three Chinese nationals were among the dead.

South Korean president Yoon Suk Yeol has declared a week of national mourning and ordered flags at government buildings and public offices to fly at half-mast.

Mr Yoon, who has visited the scene, called for officials to investigate the cause of the accident and review the safety of other large cultural and entertainment events to ensure they proceed safely.

The crowd surge is the country’s worst disaster in years.

In April 2014, 304 people, mostly high school students, died in a ferry sinking.