China has signed $6 billion mining and construction deal with Sierra Leone, which the west African nation said Thursday would boost an economy still recovering from an 11-year civil war.

The private China Kingho Group will build a $1.7 billion north-south railway stretching 250 kilometres (155 miles), an industrial park, a deep water port for the transportation of ore to China, and a "mineral resources project", a government statement said, without elaborating.

Sierra Leone remains one of the world's poorest countries after the conflict which ended in 2002, but its mineral riches -- which include diamond, gold, bauxite, titanium ore and magnetite iron-ore -- have attracted massive investments.

Sierra Leone mineral resources minister Minkailu Mansaray said coal miner Kingho, which already has mining and construction interests in Sierra Leone, "remains a key player in the country's development".

"As a government, we will continue to encourage investors which are reliable, committed and trustworthy to beef up our economy," the minister said.

Kingho chairman Huo Qinghua noted that "with the signing of the agreement, Sierra Leone will have the lion's share of the company's investment, economic growth and other social amenities".

The railway from the northern mining district of Tonkolili to the southern coastal town of Sulima will be the second in Sierra Leone funded by China.

Iron ore miner African Minerals owns a 120-km line built by another Chinese firm which transports raw ore to a specially constructed port in the north of the country for export.

The authorities did not disclose the timeframe of the projects.