Pakistan's Punjab declared a health emergency due to toxic smog on Friday, banning construction, shutting schools for another week and moving universities online, with a three-day lockdown possible, the province's senior minister said on Friday.

Air quality in Lahore reached hazardous levels this week, while other cities in South Asia also battle toxic pollution.

The authorities have also imposed a "health emergency" in Lahore and Multan districts to combat dense smog blanketing the province of about 130 million population for the last few weeks

Cities across India and Pakistan are struggling with dense smog that has worsened air quality, with authorities declaring a "health crisis" in the latter's Punjab province.

According to the provincial health department, around two million cases of respiratory disease, besides complaints of asthma, chest infections, conjunctivitis and heart issues, have been reported in hospitals during the last month.

A Pakistani province declared a health emergency Friday due to smog and imposed a shutdown in two major cities. Smog has choked Punjab for weeks, sickening nearly 2 million people and shrouding vast swathes of the province in a toxic haze.