CONAKRY, Aug 1 (Reuters) - Guinean President Lansana Conte sacked one of his government's most powerful ministers on Friday, in what some analysts said was fall-out from a dispute with mining giant Rio Tinto <RIO.L>.

No official reason was given for the removal of Mamady Sam Soumah, who held the post of secretary general of the presidency. State television said he would be replaced by Alpha Ibrahima Keira, the president's son-in-law.

Analysts say Soumah has been involved in complications over Rio Tinto's planned $6 billion Simandou project. The company has said the importance of the mine, which should deliver 70 million tonnes of iron a year, "cannot be overstated".

The company received notice on Friday purporting to rescind the concession. Soumah signed a letter from the presidency in June querying the validity of the project.

"It seems that he (Soumah) has paid today for his tumultuous relationship with Rio Tinto," a source at the presidency told Reuters, adding that Conte's office was rife with infighting.

Rio Tinto said on Friday it was confident that it had complied with its obligations over the Simandou mine and was analysing issues raised by the presidency with the International Finance Corporation, its partner in the project.

Guinea is rich in iron ore, bauxite, gold, diamonds and other minerals, all of which are attracting the attention of investors, not least from China, which is looking at a multi-billion dollar mines-for-infrastructure deal. (For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com) (Reporting by Saliou Samb; writing by David Lewis; Editing by Elizabeth Piper)

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