Vietnam needs about $15.6 billion to invest in major bauxite and alumina refining projects by 2025, to make use of its vast, and largely unmined, bauxite ore reserves, the government said on Wednesday.

The country's bauxite ore reserves, the world's third-largest after Guinea and Australia, are estimated at about 5.5 billion tonnes, 62 percent of which is located in the central highland province of Dak Nong, Prime Minister Nguyen Tan Dung said in a government directive.

Bauxite is a clay compound used to produce aluminium.

Dung has asked relevant authorities to set up shareholding companies in which Vietnamese entities would hold majority stake to mine and process the minerals.

A host of foreign companies have expressed interest in investing in Dak Nong, the bauxite hub, including China's Chalco, Alcoa Inc. of the United States and Russian firm United Company RUSAL.

Dung said in the directive that up to $13.7 billion would be invested in seven plants by 2015 to produce 8.4 million tonnes of alumina per year and 650,000 tonnes of aluminium oxide, as well as two aluminium refineries by 2025.

A sea port for 50,000-tonne vessels and a railway linking its central highlands with the sea port, needing a total investment of $1.9 billion, will be built in the south-central province of Binh Thuan as part of the infrastructure, he said.