At around 10.30 pm, several large boulders fell into a residential area along Le Loi Street in Hop Tien Village, Chi Lang Commune, affecting a stretch of about 300 metres.
One boulder damaged the porch of a two-storey house, while another smashed through a home and rolled into its living room, damaging property. No casualties were reported.
Local authorities and emergency teams evacuated 14 households from the danger zone overnight. They continued to inspect the site on August 24 to identify the landslide area and assess further risks.
Residents have been advised to avoid the affected section of road.
The incident came amid prolonged heavy rain and flooding in Lang Son, which had killed one person as of 5 pm on August 23. The victim, born in 1999, was buried when a landslide caused his house to collapse in Thai Binh Commune.
More than 4,030 homes and auxiliary structures across the province have been affected, including over 360 damaged by landslides or strong winds and 3,620 flooded.
Floodwaters have inundated residential areas in several localities due to the impact of Storm Narra, while around 1,300 traders at Gieng Vuong and Ban Nga markets in Ky Lua Ward have been affected.
More than 900 landslide and flooding sites have been reported along roads, leaving some areas temporarily isolated and hampering rescue operations.
Authorities have evacuated more than 2,625 households from areas at risk of severe flooding and landslides.