Punjab, Pakistan's most-populous province, has imposed a ban on almost all open-air activities and ordered stores, markets and malls in some areas to close early as high levels of air pollution cause an unprecedented rise in smog-driven illnesses.

Schools have also closed in the main cities of the province, of which Lahore is the capital, with all the restrictions to run until November 17.

Earlier this month, Lahore, which regularly ranks among the world's most polluted cities, had an air pollution index score of 1,900 in some places, according to Swiss group IQAir.

Although the level is now lower, its index score of more than 600 on Monday still means that residents are breathing highly toxic air, with 0-50 considered the target score.

What did the Punjab government say?

"The spread of conjunctivitis/pink eye disease due to bacterial or viral infection, smoke, dust or chemical exposure is posing a serious and imminent threat to public health," the Punjab government said.

It said open-air sports events, exhibitions, festivals and restaurant dining were prohibited, but "unavoidable religious rites" could still occur.

Pharmacies, oil depots, dairy shops and fruit and vegetable shops are also allowed to stay open beyond the 8 p.m. local time closing time stipulated in the directive.

What is causing the smog?

Air pollution rises each winter in several regions of South Asia as cold air traps dust, factory and vehicle emissions and smoke from stubble burning on farms.

In addition, the Punjab government is blaming the air pollution crisis this year on neighboring India.

The pollution problems there have been made worse by the smoke emitted by firecrackers set off on Diwali, the Hindu festival of lights celebrated on October 31 this year, despite a ban.

Children at risk

On Monday, UNICEF called for more to be done to save children from the deleterious effects of air pollution.

The UN's child protection agency said the toxic air in the region was putting more than 11 million children below five years of age at risk.

"In addition, schools in smog-affected areas have been closed ... the learning of almost 16 million children in Punjab has been disrupted," said Abdullah Fadil, UNICEF representative in the country, adding that the country could ill afford more learning losses.

The WHO says that air pollution can trigger strokes, heart disease, lung cancer and other respiratory diseases.

Children, especially babies, and the elderly are the groups most at risk.

tj/rmt (Reuters, AFP)