Forest fires that have killed 26 people and left thousands homeless in south-central Chile in the past week threatened new regions Tuesday as temperatures soared.

Some 5,600 firefighters, the majority of them volunteers, are actively battling 81 priority blazes out of 301 still burning, according to authorities.

As international help in the form of personnel and equipment boosted the teams' efforts, officials declared a red alert in the southern region of Los Rios where fires threatened the Corral and Valdivia municipalities.

Officials also fear fires could break out in the metropolitan region around the capital, Santiago.

After a brief reprieve over the weekend, temperatures soared again Tuesday to create conditions that, combined with the effects of a devastating drought, are conducive to fire spread.

The mercury in many places was likely to exceed 37 degrees Celsius until the end of the week, according to forecasts.

"A very complex climate situation can arise," said deputy interior minister Manuel Monsalve, urging teams to be "prepared for any eventuality."

More than 2,100 people have been injured in a week of blazes in the regions of Biobio, La Araucania and Nuble, where a state of emergency is in place.

Flames have consumed more than 280,000 hectares of land, an area larger than the country of Luxembourg, and razed 1,150 homes, according to the Senapred national emergency response service.

The smoke cloud covering much of Chile as a result has also triggered health warnings.

Fifteen people have been arrested on suspicion of setting some of the fires.