floods in chile march 2015
© ReutersThe torrential downpours prompted the Chilean government to issue a red alert for the Atacama region.

Flooding caused by the heaviest rains to hit northern Chile in decades has left at least three people dead and 22 missing, officials say.

The torrential storms, which began late on Tuesday, also caused mudslides and rivers to breach their banks, stranding thousands of residents.

Chile's national emergency office (ONEMI) said nearly 61,000 people were without power and almost 50,000 lacked drinking water in the usually arid regions of Coquimbo, Atacama and Antofagasta.

Two of the fatalities were in the Atacama region while the third was in the neighbouring city of Antofagasta, the deputy interior minister said.

Twenty-two people were reported missing.

President Michelle Bachelet travelled to the affected areas to assess damage and help lead rescue efforts.

"We're doing everything humanly possible to get to where [those affected by the catastrophe] are as quickly as possible," Ms Bachelet said.

The government declared a state of emergency, ordering the military to coordinate support operations and take control of public order in the Atacama area.

Many roads were cut off and evacuations in several towns were carried out using air transport, deputy minister Mahmud Aleuy said.

The normally arid north is home to many of Chile's largest copper mines, which account for about a third of global supply.

The torrential downpours forced companies to suspend operations at several of the area's major mines, putting an estimated 1.6 million tonnes of capacity of the red metal on hold.

floods in chile march 2015
© AFP: Alex FuentesA resident wades across a flooded street in the city of Copiapo in northern Chile.

Fibre optics had been cut across the northern region, which was affecting communications and could affect flights, said LATAM Airlines' Chilean arm LAN.

The sudden autumn downpour comes after an unusually hot, dry summer exacerbated an eight-year drought and left fields parched.

The dry conditions continue in the south of Chile, where firefighters are battling nearly 40 separate blazes that are burning some 14,000 hectares, according to ONEMI.