UPDATE 1-Trafigura sells 20 pct stake in Puma to Angola

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LONDON, Sept 29 (Reuters) - Trafigura, one of the world's top oil and commodities trading houses, said on Thursday it had agreed to sell a 20 percent stake in its mid and downstream unit Puma Energy International to Angola's Sonangol Holdings.

"This transaction is an important first step in the group's strategy to open up its capital to strategic and public investors alike," Trafigura said in a statement.

The value of the transaction was not disclosed.

Sonangol Holdings LDA is a subsidiary of Angola's state run oil firm Sonangol E.P.

Sonangol already has 10 percent of retail units in Southern Africa, which Puma bought from oil major BP last year. (Reporting by Ikuko Kurahone; editing by James Jukwey)