Thousands of Mongolians have protested for the second time this winter to call attention to government inaction on air pollution.

A protest Saturday drew an estimated 7,000 people, many of them wearing air masks underneath thick winter hats. The protesters braved temperatures that fell below minus 20 degrees Celsius (minus 4 Fahrenheit). Standing in the city's central square, they held black balloons and protest signs.

Ulaanbaatar is one of the world's coldest capitals, and more than half of the city's 1.3 million residents rely on burning raw coal, plastic, rubber tires and other materials to stay warm and cook meals.

In impoverished neighborhoods that ring the city, many live in traditional round tents without heating, leaving them to burn polluting fuels.

The protesters say the government hasn't helped.