Belgian King Philippe (R, Front) and Queen Mathilde (L, Front) attend a tribute ceremony in Verviers, Belgium, on July 20, 2021. Belgium observed a national day of mourning on Tuesday to pay tribute to the victims of last Wednesday and Thursday's deadly floods in the country. (Photos: Xinhua)

Rescue workers attend a tribute ceremony in Verviers, Belgium, on July 20, 2021. Belgium observed a national day of mourning on Tuesday to pay tribute to the victims of last Wednesday and Thursday's deadly floods in the country.

Belgian King Philippe (C-R) and Queen Mathilde (C-L) attend a tribute ceremony in Verviers, Belgium, on July 20, 2021. Belgium observed a national day of mourning on Tuesday to pay tribute to the victims of last Wednesday and Thursday's deadly floods in the country.

People attend a tribute ceremony in Verviers, Belgium, on July 20, 2021. Belgium observed a national day of mourning on Tuesday to pay tribute to the victims of last Wednesday and Thursday's deadly floods in the country.

Belgian Prime Minister Alexander De Croo (Front) attends a tribute ceremony in Verviers, Belgium, on July 20, 2021. Belgium observed a national day of mourning on Tuesday to pay tribute to the victims of last Wednesday and Thursday's deadly floods in the country.