TOKYO, Nov 19 (Reuters) - A fire ripped through more than 170 buildings and killed one person in a southern Japanese coastal city on Wednesday, with military and firefighting helicopters scrambling to extinguish the country's largest urban blaze in almost half a century.

Aerial footage from broadcasters showed houses reduced to rubble and thick plumes of smoke rising from the hilly Saganoseki district of Oita city, which overlooks a fishing harbour renowned for its premium Seki-brand mackerel.

The flames had also spread to nearby forested slopes and an uninhabited island more than one kilometre off the coast, likely due to strong winds, local media reported.