Brent oil futures jumped 2% to top $93 a barrel on Tuesday, widening its premium against US crude as a growing strike by oil workers in Norway tightened North Sea supplies.
In Norway, the world's No. 8 oil exporter, Statoil said it was shutting four more oil platforms in the North Sea due to the strike that began on Sunday, initially hitting two oil fields.
So far, the action has cut Norway's oil production by 150,000 barrels per day.
The disruption helped pushed out international benchmark Brent futures premium to US crude by more than $1.80 in late trade to $13.66.
In London, Brent crude for August delivery rose $2.01 to settle at $93.02 a barrel. Trading picked up considerably late in the session, pushing up Brent to a session high of $93.17, highest since June 20.
"Brent crude is up due to the ongoing strike by Norwegian oil workers that has shut some production," said Gene McGillian, analyst at Tradition Energy in Stamford, Connecticut.
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US August crude settled up 15 cents at $79.36, after being down most of the session, having fallen to a low of $78.36 early, then gaining in late trade as US stocks rose.
Brent's strength rubbed off on US heating oil futures, with the front-month July contract rallying to close up 1.5% at $2.5765 a gallon.
"A more expensive Brent for a weak EU is going to mean it is cheaper to import distillates from the US rather than trying to make it there," said Carl Larry, president of Oil Outlooks LLC in New York.
Trading volumes were light, reflecting caution ahead of the EU summit that begins on Thursday. Brent volume outpaced US crude's and was up about 8% from its 30-day average, according to Reuters data. US crude volume was down 22%.
In post-settlement trading, prices were little changed after the American Petroleum Institute reported that US crude stockpiles rose 507,000 barrels last week, defying the forecast in a Reuters poll for a 500,000 barrel decline.
In earlier trade, expectations of a crude stock drawdown had supported the rise in oil futures on both sides of the Atlantic.
The API data also showed that gasoline stocks rose 373,000 barrels, less than expected, and distillate stocks fell 1.0 million barrels, slightly less than forecast.
The US Energy Information Administration will issue its own inventory report on Wednesday, at 10:30 am EDT (1430 GMT).
EURO ZONE, INVENTORIES
Persistent worries about the euro zone debt crisis and fading hopes that a summit of European Union leaders this week will find a lasting solution have weighed on prices this month.
The two-day EU summit begins on Thursday and savvy investors are cooling their heels ahead of the meeting before making bets. While many expect little firm action to resolve the euro zone crisis, any signal of more cooperation to ease the crisis may be seen as positive and spur buying of riskier assets such as oil, analysts said.
"It's difficult to become too bullish given the uncertainty still in Europe and the expiration of (US) product futures later this week," said Tom Pawlicki, analyst at trading platform EOXLive.com.
In early trade, rising tensions between Syria and Turkey helped lift oil futures. NATO member states condemned Syria for its shooting down of a Turkish military jet last week and Ankara warned Damascus against any further military moves.