VALPARAïSO, Chile (AFP) - Four people have died in a huge fire that on Sunday was consuming the outskirts of Chile's port city of Valparaiso and was advancing unchecked towards its Unesco-listed historic centre, destroying hundreds of homes along the way and forcing the evacuation of more than 3,000 people.
The military has taken over security in the city, located on the Pacific coast 110km north-west of the capital Santiago and with a population of 270,000, after the government declared it a disaster zone.
"This is the worst catastrophe Valparaiso has ever seen," the regional government administrator Ricardo Bravo told local reporters.
Many residents overnight watched, helpless, from distant vantage points as the hills burned bright red. Thick smoke clouded the sky.
Hundreds of firemen, including ones dispatched from the capital, were hopelessly outmatched in their battle to limit the spreading disaster. They were forced to retreat time and again as flames reduced more than 500 homes to cinders, a wall of red towering above them.
The massive tongues of flame were advancing down the slopes of the city towards its port and heritage-listed center, driven by strong winds.
"We have four people dead - three men and a woman," Interior Minister Rodrigo Penailillo told Radio Cooperativa on Sunday, giving a provisional death toll.
He added that more than 700 people forced to leave their homes had been received in nearly a dozen temporary shelters.
The city is spread out over more than 40 hills, hindering emergency vehicle traffic.
"My brother's house was entirely burnt. We had only finished it two weeks ago. We tried to save something but it was truly an inferno," one resident Cristobal Perez told the Chilevision television network.
"I started to become overcome by the smoke along with my two dogs. It was terrible - impossible to breathe," another resident told the channel.
The vast blaze has caused cuts to power and drinking water in many areas of Valparaiso.
More than 200 inmates at a women's prison were evacuated due to "large amounts of smoke produced by the fire", said Mr Tulio Arce, the regional prison guard director.
The cause of the fire, which began in woodland near the city late on Saturday, was being investigated.
Chile's Interior Minister said the disaster decree issued on Saturday by President Michelle Bachelet activated an "exceptional" constitutional provision allowing the military to be called in to help.
The navy, which has a major base in the port city, immediately responded by taking over security. It deployed uniformed personnel into the streets to maintain order and to help with the evacuations.
Valparaiso is one of Chile's most important ports. It lived its era of glory from the mid-19th century to the early 20th century as a stopover point for ships steaming down South America and to round its southern tip into the Atlantic Ocean.
The center of the city still features the many colored houses dating from that period, built by European immigrants. Its cobbled streets and funicular trams running up near-vertical rails supported its 2003 listing as a Unesco-protected heritage site.
Fires occur frequently in central Chile, where summer sends temperatures soaring. In February 2013, some 105 homes were destroyed in Valparaiso, affecting 1,200 people, after a 27-year-old man started a blaze.