Brent crude prices rose on Thursday, recovering from a six-week low and halting a three-day slide of more than 7 percent, while U.S. crude seesawed in choppy trading as the front-month October contract approached expiration.
Lending support to the oil futures complex, U.S. gasoline futures rallied 2 percent, supported by a fire at Venezuela's El Palito refinery and a decline in the U.S. gasoline inventory, reported by the government on Wednesday.
Heating oil futures gained more than 1 percent.
The Venezuelan fire followed last month's blaze at the OPEC member's Amuay refinery. The U.S. Energy Information Administration (EIA) said domestic gasoline stocks fell 1.41 million barrels last week.
Brent's drop to $107.10 a barrel early on Thursday, the lowest price since August 3, pegged the retreat from last Friday's settlement at more than $10.
"We do regard the scale and above all the speed of the price slide as excessive," a Commerzbank research note said. "We expect to see a counter-movement in the next few days."
Brent's premium to U.S. crude tested below $16 a barrel and found support above the $15.50 level a fourth straight day, then bounced back above $17. Wednesday's $15.57 low was the narrowest spread since July 25, according to Reuters data.
Brent November crude rose $1.50 to $109.69 a barrel by 1:21 p.m. EDT (1721 GMT), having reached $109.84.
U.S. October crude, with the contract set to expire at session's end, was up only 7 cents at $92.05 a barrel, after slipping to $90.66, just below the 100-day moving average of $90.73 and the lowest price since August 6.
U.S. November crude rose 3 cents to $92.33, having swung from $90.96 to $92.69.
Total Brent trading volume outpaced U.S. turnover, with Brent 20 percent above its 30-day average, while U.S. crude lagged its 30-day average by 36 percent.
Brent reached $117.95 and U.S. crude $100.42, both four-month peaks, last Friday after the U.S. Federal Reserve's launch of a third monetary stimulus program.
But concerns about the economic weakness prompting central bank action, indications that OPEC's top exporter Saudi Arabia is working to lower oil prices, and rising U.S. crude oil inventories helped fuel this week's price slide.
U.S. crude oil stockpiles jumped 8.5 million barrels last week, the EIA's report showed, far more than expected.
Crude felt pressure on Thursday from news that the HSBC Flash China manufacturing purchasing index (PMI) for September was 47.8, well below the 50 level that separates contraction from expansion, although a shade higher than the nine-month low of 47.6 reached in August.
The weak China factory data came a day after the Ministry of Commerce said the export outlook in the world's No. 2 oil consumer was poor and demand would remain weak in the next few months.
"If China hits a wall, and Europe falls out from under us, then we're going to be falling back into a recession, and that could be worse than the Great Depression," said Tony Nunan, an oil risk manager at Mitsubishi Corp in Tokyo.
But other analysts noted the weakness reflected in the data might spur government efforts to support economic growth and prompt China to launch its stimulus program, joining the U.S. and Japanese central banks.
(Additional reporting by Peg Mackey in London and Luke Pachymuthu and Ramya Venugopal in Singapore; Editing by John Wallace and Sofina Mirza-Reid)