Shanghai is China’s biggest city, financial hub, and a key driver of the entire country’s economy. Jing’an district is a central key commercial area, its to require all supermarkets and shops to shut, and residents to stay home, until at least Tuesday.Mass testing will take place from Sunday until Tuesday.
Adds Reuters:

The use of all exit permits previously given to residents that allowed them to leave their homes will be suspended, the district added without saying why.

Shanghai has been inching towards reopening, this is a setback and a risk negative at the margin come Monday.