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* FTSE 100 closes down 0.4 pct after late selloff
* Traders run for exit as Russia accuses Ukraine of selling
* RBS jumps 11 pct as UK upturn boosts results
* BSkyB falls 5.5 pct on news of 4.9 bln pound acquisition
By Francesco Canepa
LONDON, July 25 (Reuters) - Britain's main equity indexclosed lower on Friday as new tensions between Russia andUkraine and falls on Wall Street led traders to cash in on theirweekly gains just before the close.
The FTSE 100 closed 29.91 points, or 0.4 percentlower, at 6,791.55 points, erasing nearly half its weekly gainsin the last hour of trading after Russia accused Ukraine ofhaving shelled across the border.
U.S. indexes also fell, partly weighed down by weak resultsfrom online retailer Amazon and a revenue warning fromthe world's largest credit and debit card company, Visa.
Investors were reluctant to hold on to their long positionsinto the weekend as the geopolitical landscape remainsuncertain.
"There's uncertainty out there in Ukraine and the market hada bit of an exit move," Mark Priest, a senior trader at ETXCapital, said.
BSkyB was the heaviest faller on the FTSE, sliding5.5 percent, after the company placed shares representing nearly10 percent of its capital to finance part of its acquisition ofSky Deutschland and Sky Italia.
Shares in RBS, however, surged 10.8 percent, their biggestrise in four years, after the bank posted a surprise pretaxprofit for the second quarter, citing an economic upturn thatallowed it to write back losses that had been booked on badloans.
Fellow British-focused lenders Barclays and LloydsBanking Group, which are due to report next week, wereup more than 1 percent.
"Credit quality keeps improving, especially in distressedassets such as commercial real estate," said Espirito Santoanalyst Shailesh Raikundlia, who has a "neutral" recommendationon the stock.
"In general, the credit environment is pretty benign andthat should come through in banks' results."
The positive mood on the British economy was underpinned bydata showing economic output in the second quarter finallytopped levels seen before the financial crisis struck six yearsago.
Network operator Vodafone added 4.4 points to theFTSE as it rose 2.1 percent after saying its performance hadbegun to stabilise in several European markets.
Pegging back the index were export-oriented companies suchas heavyweight drugs firm GlaxoSmithKline and fashionbrand Burberry.
GSK knocked 8.9 points off the index as it faced newallegations of corruption, this time in Syria, where thedrugmaker and its distributor have been accused of paying bribesto secure business, according to a whistleblower's email.
Burberry fell 1.6 percent after French luxury goods groupLVMH posted below-forecast second-quarter sales andprofits, hit by a drop in demand from China. (Additional reporting by Lionel Laurent; Editing by SusanFenton)
