Oil prices rose strongly on Monday even though a group of eight oil-producing countries announced on Sunday that they would be increasing supplies.

The countries, led by Saudi Arabia, said in a news release that they would increase production by 137,000 barrels a day, beginning in October.

Although the new planned increase amounts only to a fraction of a percent of global supply, it sends a strong signal that the producers have shifted to a new approach after restraining production in recent years.

Prices for Brent crude rose about 1.5 percent in trading on Monday to $66.52 a barrel on the Intercontinental Exchange.

The group of oil producers began gradually increasing output in April. Oil prices initially fell on fears of supply outstripping demand, but they have since stabilized even as the producers accelerated their increases.

“The thinking is that actually being bold has been a successful strategy so far this year,” said Richard Bronze, head of geopolitics at Energy Aspects, a research firm in London.