Brent North Sea crude for delivery in September dropped 88 cents to $108.06 a barrel in London midday deals.
New York's main contract, West Texas Intermediate (WTI) light sweet crude for September, fell 42 cents to $90.98.
"Mild profit-taking is being seen, with Brent and WTI easing back from Friday's highs," said Sucden Financial Research analyst Jack Pollard.
A rally on Friday saw WTI prices surge more than four dollars to pass $91 a barrel, while Brent rose more than three dollars to within striking distance of $109.
Crude prices were weaker "after rallying on a stronger-than-expected US jobs report, while the market awaited Chinese trade data due later this week for trading cues," Phillip Futures said in a report.
On traders' watchlist for this week is the release of a slew of economic data from China which will provide an update on the economic health of the world's largest energy consumer.