BEIJING -- Air pollution worsened on Monday in many parts of northern China, with poor visibility disrupting air and ground traffic.

Tianjin airport said that from 8:30 pm Sunday to 10 am Monday they suspended service, leaving 131 flights canceled and 75 delayed.

Meanwhile, all expressways in the northern municipality of Tianjin were closed.

Local authorities in Tianjin increased public transport capacity by 15 percent to accommodate passengers, as cars have been ordered to run on alternate days for five days until midnight Wednesday.

Beijing also increased its public transport and implemented the same odd-even number plate rule.

Beijing municipal environmental protection bureau has introduced a spate of pollution reduction measures, including the vehicle restriction, to help cut PM2.5 pollutant emission by over 20 percent.

In Shandong, over 100 toll gates on four expressways were closed and some flights in the provincial capital airport were delayed by more than two hours.

Smog started to envelop Beijing, Tianjin and provinces of Hebei, Henan and Shandong over the weekend and is forecast to clear Thursday. Over 20 cities have issued red alerts for smog.

On Monday, the PM2.5 reading in many cities in northern China, mainly in Hebei and Henan, exceeded 500 micrograms per cubic meter.

The reading at one monitoring station in Shijiazhuang, capital of Hebei, exceeded 1,000 micrograms per cubic meter at 1 pm Monday.