SHANGHAI, Sept 13 (Reuters) - Authorities in Shanghai and neighbouring coastal regions cancelled flights, and suspended schools, subways and trains as Typhoon Chanthu approached mainland China after drenching Taiwan. The storm, with winds of more than 170 kilometres per hour near its eye, had been downgraded from a super typhoon to a strong typhoon on Sunday evening and was expected to gradually weaken, Shanghai city authorities said in a post on their official WeChat account. But it was still expected to bring strong winds and heavy rain to coastal regions. The province of Zhejiang near Shanghai raised its emergency response to the highest level on Sunday, closing schools and suspending flights and rail services in some cities, the official Xinhua news service reported. Zhejiang also issued red alerts for flash floods in nine districts. In Shanghai, home to about 26 million people, all flights at the city"s larger Pudong International Airport were to be cancelled from 11 a.m. local time (0300 GMT), while flights from the smaller Hongqiao airport in the west of the city were to be cancelled from 3 p.m., the Shanghai government announced on WeChat. The city also suspended subway services on some lines serving the city"s southern districts, and said parks, outdoor tourist attractions and playgrounds would be closed on Monday and Tuesday. Classes were also due to be suspended on Monday afternoon and Tuesday. Official forecasts called for rainfall of 250-280 millimetres in some areas of southeastern Jiangsu province, Shanghai and northeastern Zhejiang. Taiwan downgraded typhoon Chanthu to a medium typhoon on Saturday. The storm did not make direct landfall on the island.