Shanghai braced for a second day of severe pollution on Monday after the city's Air Quality Index hit record hazardous levels.

The city's environmental authority issued its first orange alert - the second-highest in its four-level warning system - after the index reached 317.

The concentration of PM2.5 - particulate matter smaller than 2.5 microns in diameter that can penetrate the lungs - stood at an average of 266 micrograms per cubic meter in the previous 24 hours, running from noon to noon.