Brent North Sea crude for delivery in November eased eight cents to $114.54 an ounce in London midday deals.
New York's main contract, light sweet crude for November slipped 37 cents to $91.49 a barrel.
"The supply risks which caused Brent to climb to $116 per barrel last week have given way to concerns about a cooling of oil demand sparked by more pessimistic demand estimates by the International Energy Agency (IEA) and import figures from China," said Commerzbank analyst Carsten Fritsch.
The IEA on Friday said it expected global demand for oil through 2016 to grow by half a million barrels a day less than previously estimated.
It said in its medium-term report that the oil market was now at a "crossroads" and its outlook was "against the backdrop of sluggish economic growth and increasing energy efficiency," particularly in advanced economies.
Crude oil prices last week soared to their highest levels since late September, driven by fears of an escalating crisis between Syria and Turkey.
Turkey has banned Syrian civilian flights from its airspace, Foreign Minister Ahmet Davutoglu said on Sunday, after Damascus announced similar restriction on Turkish flights.
Ankara has taken an increasingly strident line towards its neighbour since a shell fired from the Syrian side of the border killed five Turkish civilians on October 3.
The tit-for-tat flight bans came after Turkey this week intercepted a Syrian Air passenger plane from Moscow on suspicion it was carrying military equipment for the regime.
