Construction banned and schools shut as toxic air engulfs New Delhi

Masks have returned to the streets of New Delhi as residents grapple with the annual surge in air pollution in the Indian capital (Altaf Qadri/AP)

Masks have returned to the streets of New Delhi as residents grapple with the annual surge in air pollution that has engulfed the Indian capital region.

Primary schools have been ordered to shut this week and polluting vehicles and construction banned as a thick cover of smog hangs over the city.