China has reportedly built the world's largest air purifier in a bid to tackle smog.

The 100-metre-tall (328 ft) circular tower is said to be able to improve air quality within an area of 10 square kilometres (3.86 square miles), according to South China Morning Post.

Reports from the Institute of Earth Environment at the Chinese Academy of Sciences claimed that the cleaning system could reduce 15 per cent of fine particles in smog that were deemed most harmful to health.

World's largest air purifier: The 328ft tower is said to be able to filter out toxic chemicals in air

Another report from the local Xi'an Evening Post said the tower was completed in May, 2016, and had been undergoing tests to see if it could really improve air quality in the surrounding neighbourhood.

The tower and related machine parts occupy 2,580 square metres in Xi'an, the provincial capital of Shaanxi Province in north-west China.

The tower is a solar-assisted large-scale cleaning system. At the base of the tower, there are several greenhouses which could draw polluted air into the tower, purify it before releasing it back to the environment, reported South China Morning Post.

On a clear day, tall buildings in Xi'an, China, can be seen clearly from far away (file photo)

But it could turn worse once it's affected by heavy smog and the sky turned grey and foggy

Citizens have to wear masks on the street to avoid breathing too much toxic air particles

The greenhouses cover an area about half the size of a football pitch.

Dubbed as the world's largest air purifier, the tower can filter out fine particulate matter, including PM 2.5, nitrogen oxides, nitrogen dioxides as well as sulfur dioxide.

These substances prompt the formation of smog.

Cao Junji, the head researcher of the programme, told South China Morning Post the department had set up over 10 air quality monitors in the surround area to keep the record on track.

Mr Cao said the results were very encouraging, the tower was able to purify over 10 million cubic metres every day.

He added that the project would be continuing to improve its overall performance.

A smaller, seven-metre-tall (23-ft) air purifier tower was set up in Beijing two years ago

Dutch artist Daan Roosegaarde designed the 'smog free tower' to fine smog in the capital city

In Oct 2016, an invention labelled 'Smog Free Tower' was installed at a park in central Beijing.

It was thought to be the world's largest air purifier with a height of seven metres (23 ft). It could clean 30,000 cubic metres (1,060,000 square feet) of fine smog per hour.

The tower was designed and created by Daan Roosegaarde, a 37-year-old Dutch artist and innovator.

However the effect did not seem to be able to keep at an optimal level as it was entirely powered by electricity, and most of which is generated by coal-fired power plants in China.