"The dust storm is moving from northwest China to the east," an official with the China Meteorological Administration surnamed Yang told AFP, although he said the nation's regional neighbors should not suffer too many effects.

"The influence in the eastern areas will not be big because as it enters the Bohai Sea and the East China Sea it will weaken and not hit Japan very hard."

Worsening dust storms in northern China caused by soil erosion, desertification and overgrazing in grasslands have in recent years spread as far as South Korea and Japan, irritating residents there.

This week's dust storms in northwestern China's Inner Mongolia region and Gansu province were kicked up by a strong Siberian cold front that resulted in the mercury plunging in northern China.

With the passing of the dust storm, air quality in Beijing was markedly improved on Wednesday with the winds blowing out heavy pollution that had accumulated in the capital since Friday last week.

The Beijing Environmental Protection Bureau had called the accumulation the worst period of pollution to hit the capital in six years and warned elderly people and children to stay indoors and avoid strenuous activities.

Air quality in the capital reached "hazardous" levels on Sunday and Monday.

Beijing has been monitoring its air quality for several years and is seeking ways to ensure that pollution will be low during the 2008 Beijing Olympics.

But the situation appears to be worsening.

According to the city's environmental bureau, Beijing has witnessed 53 "blue sky days" since the beginning of the year, 16 fewer days than the same period last year.

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