The decision made at a video meeting on Saturday means producing 411,000 barrels per day in July, which is the same level as in May and June but is significantly higher than what was previously stated.
OPEC-plus includes Saudi Arabia, Russia, Iraq, the United Arab Emirates, Kuwait, Kazakhstan, Algeria, and Oman.
Sources tell Bloomberg that the decision was made despite objections from Russia, Algeria, and Oman.
But the heavyweight Saudi Arabia pushed through, among other things, to punish Iraq and Kazakhstan, which have produced significantly more oil than their quotas allowed for some time.
In the official justification for the increase in July, the cartel writes that it is due to "stable global economic prospects and current sound market fundamentals, which are reflected in the low oil inventories".
The new decision will most likely result in lower world market prices for oil, something that not least US President Donald Trump has requested.
In April, the oil price fell to below 60 dollars per barrel, the lowest in four years, but have since risen somewhat.
Sea oil (brent) is now at 62.78 dollars per barrel. The American WTI oil is at 60.79 dollars per barrel.
On July 6, the cartel will meet again to determine production targets for August.
