Saudi Arabia's King Salman approved the allocation of 100 billion riyals ($26.67 billion) from the kingdom's reserves to the Public Investment Fund (PIF) on Wednesday, according to a statement carried by state news agency SPA.

The funds would be used to support both foreign and local investments, particularly opportunities in the local market that would help to build the private sector, the statement said.

It did not elaborate on a timeline for the investments, but said they would be phased.

Under economic reforms announced early this year, the Saudi government said it aims to expand the PIF, founded in 1971 to finance development projects in the country, from $160 billion to about $2 trillion by transferring assets such as ownership of state oil giant Saudi Aramco.

That would make the PIF the world's biggest sovereign fund by far on paper, though not necessarily in terms of the cash it had available for investment.

The fund will increase investments abroad - in June, it bought a stake in U.S. ride-hailing firm Uber for $3.5 billion — but it will still focus much of its attention on local projects designed to reduce Saudi Arabia's reliance on oil exports.

On Monday, the fund announced plans to buy a major stake in Adeptio, the Gulf-based investment firm which controls Kuwait Food Co (Americana).

It is also set to take over a stalled financial district project in Riyadh and to buy a stake in the King Abdullah Economic City north of Jeddah.