NEW YORK -- Oil prices declined on Monday as investors grappled with continued concerns over weak demand outlook.

The West Texas Intermediate (WTI) for October delivery lost 7 cents to settle at $37.26 a barrel on the New York Mercantile Exchange, while Brent crude for November delivery slid 22 cents to $39.61 a barrel on the London ICE Futures Exchange.

The moves came after the Organization of the Petroleum Exporting Countries (OPEC) lowered its forecast for global crude demand.

In its closely-watched monthly report on Monday, the OPEC said "in 2020, the global oil demand contraction is revised down further by 0.4 mb/d (million barrels per day), now contracting by 9.5 mb/d, to average 90.2 mb/d."

For the week ending Friday, WTI crude futures dipped 6.1 percent and Brent logged a weekly loss of 6.6 percent.