Vehicles move on a highway as smog envelops the areas of Lahore, Pakistan, on Thursday. AFP

The decision came after the country’s second-largest city, with a population of 11 million, was repeatedly ranked the world’s most polluted city. Doctors advised people to wear face masks and stay at home. Residents said many people were coughing and having breathing problems.

“Wearing of marks and staying at home are the two easiest solutions to avoid getting rushed to hospitals with respiratory-related diseases, infections in eyes and skin diseases,” said Salman Kazmi, a doctor at Lahore’s main Mayo Hospital, where thousands of people were treated for such ailments this week.

On Thursday, the concentration of PM 2.5, or tiny particulate matter, in the air approached 450, considered hazardous.

Experts say the burning of crop residue at the start of the winter wheat-planting season is a key cause of the pollution.

Lahore was once known as the city of gardens, which were ubiquitous during the Mughal era of the 16th to 19th centuries. But rapid urbanisation and surging population growth have left little room for greenery.

As Punjab authorities imposed an emergency in the province due to smog, a traders’ body on Friday accused the police of forcing businesses to close in Lahore, which they alleged were in defiance of government directives, Dawn News reported.

Parts of Punjab have been enveloped in smog, which contains unhealthy PM2.5 at much higher levels than the WHO annual air quality guidelines, according to IQAir.

Earlier this week, the provincial government declared a smog lockdown as part of its “environmental and health emergency” in eight cities — Lahore, Nankana Sahib, Sheikhupura, Kasur, Gujranwala, Hafizabad, Sialkot, and Narowal — all of which have had Air Quality Index (AQI) readings beyond safe limits.

However, in a revised notification issued on Thursday, the Lahore administration granted permission for city markets and shopping centres to open on Friday, while affirming a complete closure of businesses on Saturday and Sunday.

During the day, trade body All Pakistan Anjuman Tajiran (APAT) leader Naeem Mir said the APAT met with the Lahore Commissioner Muhammad Ali Randhawa, where they agreed to keep businesses open on Nov.9 and Nov.10. He added that they had agreed to shut the markets on Nov.11 and Nov.12.

However, he claimed that police arrived in various markets, and told shopkeepers to close up, which he said was a “clear violation of the understanding between traders and the Lahore commissioner.”

Mir also alleged that the government had pledged to lift the lockdown if it rained. He demanded the authorities to honour their commitment — given that it had rained in the city and the AQI had improved as a result — and immediately announce an end to the lockdown.

According to the government notification, the markets will be completely closed on Saturday and Sunday. The banks, government and private offices, all educational institutions and parks will remain closed on Nov.10, 11 and 12.