Chile has declared a state of emergency and evacuated thousands of people as a forest fire threatened the historic port city of Valparaiso, where 15 people died in blazes last year.

The fire that began in the afternoon on Friday could also reach the port of Vina del Mar as flames were spreading quickly by high winds blowing towards the Pacific.

Chilean Deputy Interior Secretary Mahmud Aleuy said about 4,500 people in six neighbourhoods had been evacuated as flames advanced nearby and that an additional 10,000 might need to be moved. About 220 hectares have so far burned in the hills above Valparaiso, according to the government.

Aleuy said some buildings had been burned but the extent of damage had not yet been determined.

Forest fires are common in Chile around March time, and have been bad this year after a hot, dry summer.

Chile suffered its worst urban fire in the same general area a year ago. Last April, a raging blaze that started as a forest fire leaped from hilltop to hilltop in Valparaiso, killing 15, injuring more than 500 and destroying more than 2,900 homes.

Chilean authorities said the current fire had lower temperatures thus far, and that winds were lower, giving firefighters a better chance to quell the blaze.