This aerial view shows the tops of high-rise buildings poking out from heavy fog in Yangzhou, in China's eastern Jiangsu province. The authorities in the city issued a red alert - the highest level - for heavy fog yesterday, with visibility reduced to 50m. Sections of several highways in Yangzhou have been closed temporarily and are being monitored for safety reasons, the authorities said, adding that drivers should turn on fog lights and reduce their travelling speed. The provincial weather bureau also issued fog alerts for other cities, including Nanjing, Taizhou, Nantong, Xuzhou and Lianyungang.