TIANJIN, March 26 (Xinhua) -- North China's Tianjin Municipality on Monday raised its smog alert from yellow to orange, the second highest level.

The orange alert took effect at 2 p.m. Monday, with heavy vehicles restricted based on odd-even license plate numbers, the municipal environmental protection bureau said in a statement.

Industrial plants were ordered to reduce emissions to ensure that major pollutants of the municipality were cut by 50 percent under the alert.

All schools were advised to suspend outdoor activities, it said.

The city has a four-tier color alert system for air pollution, with red being the highest, followed by orange, yellow and blue.

The neighboring Beijing Municipality also issued an orange alert, forecasting heavy air pollution from Monday to Wednesday.