Oil prices settled lower as traders weighed a planned release of emergency oil and diesel stocks by the Group of Seven countries against renewed attacks around the Strait of Hormuz and persistent Middle East supply risks.

December Brent crude futures fell 1.9% Monday to $100.32 a barrel, while December West Texas Intermediate futures slid 1.8% to $89.43 a barrel. Brent crude has now settled lower for three out of the past five trading sessions, while WTI has finished lower for two straight days, according to data from FactSet.

The G-7 countries agreed Friday to implement a coordinated release through the International Energy Agency of 100 million barrels of crude oil and fuel over four months, including a substantial diesel release in the first 20 days. The group also pledged not to restrict energy exports between member countries.

The IEA said around 325 million barrels of the 400 million barrels pledged under its collective action announced in March have so far been released. While Middle East crude exports have recovered significantly, refined-product flows remain severely constrained, particularly diesel, the agency said.

The U.S. Department of Energy said Monday that 800,000 barrels of crude were released from the Strategic Petroleum Reserve last week, with releases during September marking the smallest total in six months. The DOE said that there were 283 million barrels held in the reserve as of Friday, the lowest since October 1982.

Saudi Aramco cut the official selling price for November shipments of its Arab Light crude to Asia by $3 a barrel, widening its discount to the Oman/Dubai benchmark to $5 a barrel. The move came as crude flows through the Strait of Hormuz continued to recover, while freight costs remained elevated.

Continued tanker attacks, infrastructure disruptions and vessels operating without visible tracking signals are factors limiting export flows through the Strait, MUFG analysts said Monday. Saudi Arabia's latest crude-price cuts also point to improving supply conditions, they said.

Meanwhile, seven members of the Organization of the Petroleum Exporting Countries and its allies, including Saudi Arabia and Russia, agreed Sunday to keep production levels steady in November.

OPEC's Joint Ministerial Monitoring Committee separately expressed concern over attacks on energy infrastructure and disruptions to international maritime routes, saying they threaten supply availability and increase market volatility.

Despite those risks, Saudi Arabia is loading crude from both its Persian Gulf and Red Sea coasts as regional exports recover. Saudi crude shipments through the Strait of Hormuz climbed from around 1.4 million barrels a day in late August to around 4.1 million barrels a day last week, Kpler ship-tracking data showed. The kingdom's East-West pipeline has also returned to flows of around 5.5 million barrels a day after being shut in mid-September following drone attacks, leaving roughly 4 million barrels a day available for export from the Red Sea port of Yanbu, Kpler estimated.

But the recovery in export flows remains vulnerable to renewed shipping disruptions. U.K. Maritime Trade Operations said Sunday that a tanker in the Strait of Hormuz was struck by an unknown projectile, damaging its engine room. The crew was reported safe and no environmental impact was reported.

The latest attack came amid a renewed wave of incidents threatening the recent recovery in Middle East crude exports. Seven vessel attacks have been reported around the strait since Sept. 28, The Wall Street Journal reported. Gulf producers had pushed crude shipments back toward prewar levels using shuttle tankers and alternative export routes.