How is smog affecting cities in Pakistan?

Several parts of Pakistan, including the city of Lahore, are currently facing huge amounts of smog at record levels.

The conditions have had a big impact on people living there and residents have been told to stay indoors.

There have been primary school, park and zoo closures, among other restrictions as smog continues to affect the area.

Some types of vehicles, including ones that produce lots of smoke, have been banned from the worst affected areas.

"This is not just fog. It is smog, a dangerous type of air pollution that is making it hard for people here to breathe," BBC reporter Iftikhar Khan told Newsround.

"The situation here is so bad that all the schools, universities and even the parks have been closed."

How widespread is the smog problem?

The smog cloud, over the snow-capped mountains near India and Pakistan, can be seen from space in this Nasa photo

Parts of India, including the capital Delhi, have also been impacted by smog.

The smog cloud affecting South Asia is now so big it can be seen from space.

Just over two weeks ago, Lahore - Pakistan's second-biggest city - became the world's most polluted city, when the Air Quality Index (AQI) hit hazardous levels.

Today, the 14 million people living in the city continue to suffer as smog levels hit new record levels.

Children are affected by smog outdoors

According to the International Air Quality Index Scale, an index value of 300 or higher is "hazardous" to health, and Pakistan has regularly tipped over 1,000 on the scale over the past months.

"You can't even open your doors and windows, because then the smog comes in and it's terrible," said Rafia Iqbal, who is a primary school teacher.

What's caused the smog in India and Pakistan?

Fires are a big cause of the smog problem

Images from US space agency Nasa also show one of the major causes of the smog - fires.

The fires are from farmers in both Pakistan and India, burning leftover crops as a quick way to clear their fields ready for the next season.

As well as the fires, a lot of the air pollution in Lahore comes from its five million motorbikes and millions of other vehicles’ exhausts.

Industries in the city’s outskirts - like the coal-fired brick kilns - also add pollution to the air.

How long will the smog last?

Pakistani security officials have been checking for vehicles which produce lots of smoke in the worst affected areas

"The government has taken steps like shutting the factories and finding the smoke producing vehicles and even created artificial rain in some areas," said Iftikhar.

However, it's expected people living in the affected parts of Pakistan will be dealing with the pollution for a while.

"The smog is not going anywhere. Experts warn it will stick around until the end of January."