OPEC members Nigeria and Venezuela will reduce their oil production by a combined 170,000 barrels per day from Sunday, a spokesman for OPEC said on Friday.
The spokesman said the decisions were made voluntarily by each producer, insisting they were not imposed by the Organization of Petroleum Exporting Countries.
"Venezuela has formally informed OPEC that it will be cutting voluntarily production by 50,000 barrels a day as of 1st of October," OPEC spokesman Tarek Amin said.
"Nigeria will cut their production by five per cent, which is around 120,000 barrels a day. These are both voluntary cuts, these are not cuts made by the Organization."
A cut in output is seen aimed at supporting traded oil prices, which slumped by about 20 per cent in recent weeks owing to easing supply concerns.
Earlier on Friday, OPEC said that only Nigeria had decided to voluntarily reduce its output.
"There is no (OPEC) agreement, there is no formal or even informal agreement (to cut output) and what Nigeria has done is simply for its own marketing strategy," an OPEC spokesman had said.
The oil-producing cartel later revealed that Venezuela, the only South American member of OPEC, was also to slash output.
Press reports said on Thursday that several leading OPEC members, including Nigeria, Saudi Arabia and Kuwait, had informally agreed to lower their production from October because of the fall in oil prices.