SKOPJE, North Macedonia (AP) — Thousands of protesters across North Macedonia took part in demonstrations Tuesday to demand better air quality in cities that are among the most polluted in Europe.

In the capital, Skopje, demonstrators gathered outside the Environment Ministry, some wearing gas masks to highlight the problem blamed by authorities for some 3,500 premature deaths annually.

Pollution levels often spike during the winter months due to the widespread use of log fires. Many urban households, unable to afford central heating, burn wood, old tires, plastic and other waste materials, releasing a toxic mix of harmful chemicals.

Protest organizers called for rare national action after winter weather brought another spike in air pollution levels. They demand stricter government regulation of traffic and industry, citing decades of neglect.

Gorjan Jovanovski, a prominent environmental campaigner who created a mobile app to monitor air quality, said pollution was forcing city-dwellers to flee as “ecological migrants.” “It’s enough! We have waited decades for governments to act, but they’ve done nothing,” Jovanovski said.

According to European Union health authorities, pollution levels in Skopje and other Macedonian cities often exceed World Health Organization's limits by more than four times.

Several thousands joined Tuesday's protests that were organized by Green Human City, one of several environmental campaign organizations largely focused on air pollution.