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.

A Pakistani province declared a health emergency on November 15 due to smog and imposed a shutdown in two major cities.

Pakistan's Punjab province declared a health emergency due to toxic smog on Friday, banning construction, shutting schools for another week and moving universities online, while hundreds of thousands of Muslims prayed for rain and forgiveness.

With smog intensity escalating in Lahore at the end of October, affecting its 13 million residents, the Punjab government imposed a “green lockdown” and set up a “smog war room.”

One doctor compared breathing in Pakistan's toxic air to smoking "dozens of cigarettes a day" as Lahore is the world's most polluted city this week.

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.

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

The U.N. children’s agency is warning that the health of 11 million children in Pakistan’s eastern Punjab province is in danger because of air pollution that experts say has become a fifth season in recent years.

From banning tuk-tuks and barbecues to demolishing old brick kilns, Pakistan's government is pushing a series of measures to fight record-breaking smog.