US benchmark West Texas Intermediate for October delivery eased 15 cents to $95.81 while Brent crude for October rose one cent to $102.80 in mid-morning trade.

"Below-consensus manufacturing surveys in China and the eurozone did not help risk appetite," French bank Credit Agricole said in a note.

China on Monday said its official purchasing managers' index (PMI) of manufacturing activity slipped to 51.1 last month. That is down from 51.7 in July -- a more than two-year high -- and the first decline since February.

Anything above 50 indicates growth and anything below suggests contraction.

In Europe, Markit's PMI of output in the 18-nation eurozone's manufacturing sector fell to 50.7 in August from 51.8 in July.

Investors are awaiting the US Institute for Supply Management's August PMI for the US manufacturing sector later Tuesday. Credit Agricole said the figure "likely edged down to 56.2", from 57.1 in July. US markets were closed on Monday for the Labor Day public holiday.

Latest US construction spending data, another key indicator of the health of the world's biggest economy, is also set for release on Tuesday.

Simmering insurgencies in major crude producers Libya and Iraq, as well as in Ukraine, a key conduit for Russian gas exports to Europe, continue to provide support to oil prices, analysts said.