(Adds details on impairment charge, special dividend,...

(Adds details on impairment charge, special dividend, background)

Aug 19 (Reuters) - Australian diversified miner South32 Ltd (S32) on Thursday posted a 153% rise in its annual underlying profit, boosted by higher realised prices for its key commodities as demand bounced back with economies reopening.

Easing curbs and a rebound in industrial activity powered prices of the miner's metallurgical coal, aluminium and manganese in the latter half of 2020, helping it offset a $728 million impairment charge on its flagship Illawarra project.

The world's biggest producer of manganese posted underlying earnings of $489 million for the year ended June 30, higher than $193 million a year ago. That beat a Citi estimate of $471.6 million.

On a statutory basis, the miner posted a loss after tax of $195 million, compared with a loss of $65 million last year, hurt by the sale of its South African thermal coal assets earlier in the year.

South32, which was spun off from global miner BHP (BHP) in 2015, also declared a special dividend of 2 cents per share, along with a final dividend of 3.5 cents, up from 1 cent last year.