In shock and grief, South Koreans are mourning the losses of innocent young lives at Saturday night’s deadly crowd surge in Itaewon. At least 154 people -- most of them in their 20s -- died in the country’s worst disaster in years.

The narrow alleyway where the fatal stampede took place is still blocked for police investigation. But not far from the disaster site, flowers, messages and beverages have been laid out on the ground in memory of the deceased.

Mourning altars have been set up in Itaewon and elsewhere across the country, where politicians, celebrities and pedestrians have been trickling by since Monday morning.

Following are some photos from a nation grieving and in mourning on Monday.

Flowers are laid at the entrance of an alleyway in Itaewon in Seoul on Monday morning, where a crowd surge left at least 154 people dead on Saturday night. (Yonhap)

A mourner lays flowers near an exit of Itaewon Subway Station on Monday morning. (Yonhap)

President Yoon Suk-yeol (right) and first lady Kim Keon-hee visit a mourning altar for the Itaewon disaster victims set up in the front of Seoul City Hall on Monday morning. (Yonhap)

A mourner is escorted out after paying his respects to the victims of the Itaewon stampede at an altar for the Itaewon disaster victims set up in the front of Seoul City Hall on Monday morning. (Yonhap)

Interior Minister Lee Sang-min (center) attends a meeting at the Central Disaster and Safety Countermeasures Headquarters in the Government Complex Seoul on Monday morning. (Yonhap)