By David Gaffen

(Reuters) - U.S. crude and gasoline inventories rose unexpectedly last week as refineries cut output, the U.S. Energy Information Administration said on Wednesday, prompting a drop in oil futures.

Crude inventories <USOILC=ECI> rose 2.5 million barrels in the week to Aug. 19, compared with expectations for a decrease of 455,000 barrels. Crude stocks on the U.S. East Coast soared 3.1 million barrels, the biggest build since February 2015.

"The report is bearish, especially relative to expectations, led by the rise in crude oil inventories that was due to the refinery utilization declines and large rise in imports," said John Kilduff, partner at New York energy hedge fund Again Capital.

U.S. crude imports <USOICI=ECI> rose last week by 449,000 barrels per day.

Refinery crude runs <USOICR=ECI> fell by 186,000 bpd as utilization rates <USOIRU=ECI> slipped 1 percentage point to 92.5 percent of total capacity, data showed.

Gasoline stocks <USOILG=ECI> inched up 36,000 barrels, compared with expectations in a Reuters poll for a 1.2 million-barrel drop.

The weekly data shows that gasoline stocks in the U.S. Gulf Coast reached a seasonal high not seen since 2013, which could reflect decreased activity due to weaker demand.

Overall, the surprising build in gasoline stocks leaves a "substantial 8.5 percent year-on-year inventory surplus in place with little time left in the driving season," said Tim Evans, Citigroup energy analyst, in a note.

After the data, U.S. gasoline futures <RBc1> turned negative and U.S. crude oil futures <CLc1> extended losses, trading 2.7 percent to $46.84 a barrel by 11:13 a.m. (1513 GMT).

Crude stocks at the Cushing, Oklahoma, delivery hub for U.S. crude futures <USOICC=ECI> rose 375,000 barrels last week, EIA said.

Distillate stockpiles <USOILD=ECI>, which include diesel and heating oil, rose by 122,000 barrels, versus expectations for a 400,000-barrel increase, the EIA data showed. Overall stocks were at their highest weekly level on a seasonal basis since 2011, the EIA said.

(Reporting by David Gaffen; Additional reporting by Barani Krishnan; Editing by Marguerita Choy)