Foreign "guest workers" drill at the Saudi Aramco oil field complex facilities on March 2003 in Shaybah, Saudi Arabia.

Saudi Arabia has set a range of income tax rates for producers of oil and hydrocarbons, the official Saudi Press Agency reported on Monday, quoting a royal decree.

The tax rate for investments exceeding 375 billion riyals ($100 billion) will be 50 percent, SPA said. It gave other rates for producers with smaller investments.

SPA did not say whether the announcement was directly related to national oil giant Saudi Aramco. Saudi authorities plan to sell shares in Aramco next year and have been considering whether to cut the effective tax rate on the company in order to facilitate the sale.

Aramco currently pays a 20 percent royalty and 85 percent tax to the government, Saudi officials have said.

