(Adds details) BEIJING, Nov 20 (Reuters) - Heavy fog enveloped Beijing and much of north China on Monday, forcing the closure of highways, delaying flights across an area as large as Britain and lifting the pollution index in the capital to one level below hazardous. Since the fog started late on Sunday, police had shut down parts of six highways near Beijing and a ring road on the outskirts of the city, Xinhua news agency said. "City roads were also affected by fog, with police called out repeatedly to deal with congestion and accidents," it added. The fog was made worse by pollutants in Beijing, where coal-fired heating systems compound construction dust and exhaust from millions of automobiles in the winter months. The pollution index read "poor" in Beijing, with "particulate matter" to blame. The next level up is "hazardous" and the local environment bureau advised citizens to stay indoors if possible. The semi-official China News Service said the fog had hit an area of 218,000 square km (84,170 square miles), spanning seven provinces in the country's north and east. Dozens of flights had been delayed, mostly those to and from cities in the coastal province of Shandong, where there had also been some flight cancellations, staff at the region's main airports told Reuters by telephone. Visibility in parts of the provinces of Liaoning, Shandong and Jiangsu had been a mere 200 metres, delaying more than 40 flights in Liaoning's capital city Shenyang, Xinhua said. "Heavy fog will continue to blanket northern and northeastern China on Tuesday, impacting local transport systems," Xinhua said. But the fog was expected to ease in Beijing and in the nearby port of Tianjin, which has closed sections of eight highways but maintained normal airport operations, on Monday evening when a cold front and strong winds are forecast to arrive.
