By Sara Sjolin, MarketWatch

LONDON (MarketWatch) -- U.K.'s benchmark stock index dropped for a second straight day on Wednesday on ongoing fears of a U.S. military invention in Syria, although oil firms got a boost from the tension as oil prices jumped.

The FTSE 100 index lost 0.4% to 6,417.15, adding to a 0.8% loss from Tuesday.

The weakness came on the back of heightened fears that the U.S. will launch a strike against Syria, after allegations that forces loyal to the government of Bashar al-Assad used chemical weapons against rebels. White House spokesman Jay Carney said on Tuesday that President Barack Obama is still consulting with allies and members of Congress on Syria, but said there "must be a response."

The uncertainty sent waves of nervousness through the financial markets with global equity markets moving sharply lower and oil prices (CLV3) jumping above $110 a barrel, the highest level in more than two years.

The move in oil prices lent support to London's oil firms. Shares of Tullow Oil PLC gained 2.4%, Royal Dutch Shell PLC added 1.7%, BG Group PLC rose 1.1% and BP PLC (BP) picked up 1%.

Mining firms, however, were among sectors on the decline. Antofagasta PLC lost 2%, Rio Tinto PLC (RIO) dropped 1.3% and BHP Billiton PLC (BHP) gave up 0.8%.

Among miners outside the main index in London, shares of Polymetal International PLC dropped 6.4% after the precious-metals miner said it swung to a loss in the first half of 2013 as revenue declined 6%.

Shares of Meggitt PLC fell 1.2% after the aerospace and defense group agreed to take over Piezotech LLC for $41.2 million.

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