Heavy smog has hit Beijing and its vast neighbouring areas, forcing the capital to issue a heavy air pollution alert just 10 days ahead of two key meetings by the nation's most powerful government bodies. Beijing, Tianjin and other provinces in northern mainland are under heavy smog on Friday, with the smog expected to last for about one week, according to China’s Central Weather Bureau. The bureau and the Environmental Protection Ministry issued the warning yesterday. “From February 21 to 23, the air quality in Beijing, Tianjin, Hebei province and the central and northern part of Shandong province will be seriously polluted, and a heavy smog would last in the following days," their statement read. From February 21 to 23, the air quality in Beijing, Tianjin, Hebei province and the central and northern part of Shandong province will be seriously polluted, and a heavy smog would last in the following days "The situation is expected to only get improved after February 27,” it said. On Friday morning, PM 2.5 readings in most of Beijing's observatory stations spiked more than 300 micrograms per cubic metre, far above the 25 micrograms considered safe by the World Health Organisation. Beijing has been under heavy smog since noon on Thursday. The municipality’s office for severe air pollution emergency issued a yellow alert that day, advising residents to take protective measures, use public transport and reduce driving vehicles. Children and the elderly are advised to stay indoors, and middle and primary schools and kindergartens to reduce outdoor activities. This was the first yellow alert Beijing issued since it put an emergency response system – with four levels of pollution forecasts ranking from blue, yellow, orange and red – into effective last October. Beijing has issued blue alerts before. It comes just 10 days before the country’s capital hosts two important political meetings: the Chinese People’s Political Consultative Conference, the national advisory body, will meet on March 3, while the National People’s Congress, or the legislature, are scheduled for talks starting on March 5. Thousands of delegates across the country are expected to attend the meetings. The city said it has strengthened checking and supervision on the key emission sites and organisations, including the coal-burning boilers, the construction sites and open-air barbecue stands. Watch: Beijing's air pollution level 'off the charts'