BEIJING - China's two largest oil producers, PetroChina and Sinopec Group, said Thursday night that the Ministry of Finance (MOF) has raised the exemption threshold on the so-called "windfall tax" on upstream oil producers to $55 per barrel of crude oil since November 2011.

The levy, described by the MOF as a "special oil sales charge", will be set at a progressive rate between 20 and 40 percent on the excess of the average realized oil price from a base of $55 per barrel, compared with $40 previously, the oil companies said.

The charge is 20 percent when the price is between $55 and $60 and will rise progressively by 5 percentage points for every $5 increase to a limit of 40 percent when the price sits above $75 per barrel.