CARACAS, March 24 (Xinhua) -- Venezuela will impose a new tax on oil companies for their "unexpected earnings" from the soaring global oil prices, President Hugo Chavez said Monday.

    "They're earning money that they haven't accounted for," Chavez said in a speech televised Monday, adding that those large additional earnings are not "a product of any extraordinary effort."

    The government has prepared a bill outlining the tax, he said, but the tax rate has not yet been determined.

    The tax will represent the fourth rise in oil taxes in as many years as part of Chavez's drive to increase revenue from the oil industry and tighten state control over oil fields.

    Over the past two years, the Venezuelan government has raised taxes for oil exploration, extraction, processing and selling to foreign companies.