BOGOTA — Colombia has appealed for international help as it battled dozens of fires burning vast swathes of the country and covering the capital in a blanket of smoke.

As hundreds of firefighters and volunteers on Thursday battled flames on the mountains around Bogota for a fourth consecutive day, schools and a university in the worst affected areas scrapped in-person classes and dozens of flights from the El Dorado International Airport were delayed or canceled due to poor visibility.

Hundreds of blazes have already been extinguished countrywide in recent weeks amid record temperatures and dry conditions linked to the El Nino weather phenomenon.

More than 6,600 hectares of vegetation have been destroyed so far, according to the National Disaster Risk Management Unit.

On Thursday, 31 fires were still raging in five regions of Colombia — at least three of them around Bogota.

President Gustavo Petro said he had ordered the "activation of international aid protocols", and announced that offers of help have already come from the United States, Chile, Peru and Canada.

He has declared a natural disaster, allowing funds to be diverted from other budget items toward containing the blazes.

In the departments of Santander and Cundinamarca, fires have consumed about 600 hectares of forest, officials said.

Authorities have warned of a "significant deterioration" in air quality in the capital city of some 8 million people, with Bogotans counseled against outdoor physical activity.

Many pedestrians were spotted wearing face masks.

"I am very worried … My God! It's terrible," resident Andrea Gomez, 48, said.

The city council advised citizens to close their windows and leave wet towels under their doors. Bogota Mayor Carlos Fernando Galan said he was in touch with the Spanish ambassador regarding possible assistance as the situation "can become more critical".

Wild animals

Hundreds of wild animals, including raccoon-like animals called coatis, porcupines, birds and frogs, have been fleeing the heat and flames in one of the world's most biodiverse countries, and spotted in growing numbers in built-up areas.

Citizens have mobilized to bring snacks and drinks to firefighters, and sharing appeals on social media to leave out water for distressed animals.

Images shared by the authorities showed a dense white smoke cloud engulfing the control tower at El Dorado, where airport officials said 48 flights were canceled on Thursday, 16 deviated to other airports and many others delayed.

Agencies Via Xinhua