Saudi Arabia has granted three foreign consortiums contracts worth $22.5 billion (16.9 billion euros) to build a Riyadh metro, the kingdom announced at a news conference in the capital late Sunday.
The consortiums are led by US, Spanish and Italian firms.
The 176-kilometre (110-mile) six-line network is aimed at easing chronic traffic congestion in Riyadh, a city of six million people.
A consortium led by US engineering giant Bechtel Corp will construct two lines worth $9.45 billion, the official SPA news agency reported.
Another consortium led by the Spanish FCC will build three of the metro lines for $7.88 billion.
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The group includes South Korea's Samsung, France's Alstom, Freyssinet Saudi Arabia, Dutch group Strukton, and engineering groups Typsa from Spain and Setec from France.
Another line costing $5.21 billion went to Italy's Ansaldo.
The lines are planned to stretch across the capital and serve the airport and the future King Abdullah Financial District.
Oil-rich Saudi Arabia also plans to invest billions of dollars in rail networks linking major cities across the vast desert kingdom.
The kingdom already has a 449-kilometre passenger line between Riyadh and Dammam in Eastern Province, with a parallel freight line linking the capital with the Gulf coast city.