Choking, toxic smog spreads across the nation to inland and coastal cities

The mainland's notorious smog has spread from major city clusters around Beijing, Shanghai and Guangzhou to inland cities in central and western provinces and in the country's north.

Several western cities including tourist hot spots Lhasa and Xian have, unusually, been shrouded in smog or dust for the last two days, while three cities in coastal Shandong province were also blanketed by smog yesterday as pollution readings went off the scale.

"This is alarming. This shows China's unsustainable growth mode is taking its toll across the whole country," said Li Bo , a senior adviser at Friends of Nature, a mainland environmental organisation.

Sandstorms hit Lhasa, 3,700 metres above sea level, on Thursday and yesterday, reducing visibility in some areas to less than five kilometres and disrupting flights at the city's Gonga airport.

Video: A view of Beijing's smog from atop the Forbidden City

Xinhua said weather forecasters expected the sandstorm would last till the weekend. It said a sharp drop in temperature, lower atmospheric pressure and accumulated airborne particles were mainly to blame. Air quality readings were off the scale on both days, with larger PM10 particles - those up to 10 microns in diameter - a major problem.