The plan to develop one of the world's biggest deposits of iron ore is a step closer after Guinea signed an agreement with a consortium to mine the resources.

The country hopes to earn $15bn (£11bn) from the giant Simandou project over 25 years, but previous efforts to develop the iron ore have been mired in claims of corruption.

The consortium includes SMB of Guinea, Winning Shipping from Singapore and Chinese investors.

Simandou is the largest known deposit of iron ore, thought to hold two billion tonnes.

The development will include the construction of a 650km (400 miles) railway line, from Guinea’s mountainous forest region to the coast.

However, a long-running legal row between the entrepreneur Beny Steinmetz and the Brazilian mining company Vale could overshadow the development.

Both have been engaged in a dispute since 2010, when Vale bought a 51% stake in assets belonging to BSG Resources, controlled by the Steinmetz family, including two blocks of Simandou.

The joint venture lost the mining rights following accusations of bribery.