Oil futures took a sudden, sharp turn higher Monday to score a monthly gain of more than 4% and settle at their highest level in nearly 6 weeks.

Prices were on track to suffer a third straight monthly loss until a U.S. government report showed a roughly 1% decline in monthly crude production and a bulletin from the Organization of the Petroleum Exporting Countries expressed the group’s concerns over the low price of oil.

October West Texas Intermediate crude CLV25, settled at $49.20 a barrel, up $3.98, or 8.8%, on the New York Mercantile Exchange. Based on the most-active contracts, prices were up about 4.4% for the month—the first gain since May. The daily settlement was also the highest since July 21.

WTI futures on Aug. 24 posted a six-and-a-half year low at $38.24 a barrel.

Including Monday’s rally, WTI prices have tallied a three-session gain of 27.5%, or more than $10 a barrel.

WTI prices rallied Thursday on news that Venezuela had been contacting other OPEC members to push for an emergency meeting to come up with a plan to stop the oil-price rout. It also rallied Friday on the back of rising tensions in Yemen.

October Brent crude on London’s ICE Futures exchange UK:LCOV5 added $4.10, or 8.2%, Monday to $54.15 a barrel, for a monthly gain of 3.7%.

Prices had been falling early Monday as U.S. equities declined, raising more concerns about a potential slowdown in energy demand, and as traders gauged the likelihood of a Federal Reserve interest-rate hike this year.

Read: Jackson Hole roundup: No clear path for Fed in September

But in an article in its monthly bulletin Monday, OPEC said the “continuing pressure on prices, brought about by higher crude production, coupled with market speculation, remains a cause of concern for OPEC and its members—indeed for all stakeholders in the industry.”

Read: OPEC says there’s “no quick fix” for low oil prices

Without oil prices at “exceptionally high prices,” OPEC is “staring at big troubles,” said Richard Hastings, macro strategist at Global Hunter Securities.

Meanwhile, in a report Monday, the Energy Information Administration estimated June U.S. crude output at 9.3 million barrels a day, down 1.1% from a revised May figure.

A separate report released earlier Monday by the EIA had already hinted at the production decline but the full report had more detailed information on state output.

“Oil markets are hungry for any evidence of a fall in production, anywhere,” Hastings said. The monthly report also offers a “stronger data point, based on their new survey method for monthly production, and it improves the reliability of their weekly production estimates.”

On Nymex, September gasoline US:RBU5 ended higher along with oil, trading up 11.9 cents, or 7.8%, to $1.64 a gallon, with the contract down about 7.4% for the month. September heating oil US:HOU5 added 9.7 cents, or 6.2%, to $1.674 a gallon, for a monthly gain of 5.3%. The September contracts expired at the close.

October natural gas US:NGV15 ended at $2.689 per million British thermal units, down 2.6 cents, or 1%. For the month, the contract lost 2.2%, but based on the most-active contracts, prices were down 1%.

Italian energy giant Eni SpA said it has discovered a “supergiant” natural-gas field off the Mediterranean shores of Egypt.