Delhi Environment Minister Gopal Rai will chair a high-level meeting on Sunday to discuss measures to be implemented under stage III of the Graded Response Action Plan, officials said here.

A layer of pungent smog enveloped Delhi-NCR on Saturday as air pollution in the region neared the "severe" zone amid adverse meteorological conditions. This prompted the Centre's air quality panel to direct authorities in the National Capital Region to immediately implement curbs, such as a ban on construction and demolition activities, under the Graded Response Action Plan stage III.

Delhi's 24-hour average air quality index stood at 397 at 4 pm, the worst since January. It was 354 on Thursday, 271 on Wednesday, 302 on Tuesday and 312 on Monday (Diwali).

GRAP is a set of anti-air pollution measures followed in the capital and its vicinity according to the severity of the situation.

It classifies the air quality in the Delhi-NCR under four different stages: Stage I - 'Poor' (AQI 201-300); Stage II - 'Very Poor' (AQI 301-400); Stage III - 'Severe' (AQI 401-450); and Stage IV - 'Severe Plus' (AQI >450).

The restrictions on construction and demolition activities will not be applicable on essential projects concerning national security, defence, railways and metro rail among others. Mining activities will also not be allowed in the region.

The CAQM further said states might impose restrictions on the plying of BS III petrol and BS IV diesel four-wheelers in the NCR considering the worsening air quality. This direction is non-binding on authorities.

The ban on construction activities is likely to affect housing projects in Noida, Ghaziabad, Gurugram and other areas.