By Carla Mozee, MarketWatch

LONDON (MarketWatch) -- Barclays PLC helped push U.K. stocks higher on Thursday after the bank said it will outline a growth strategy, aiding the main London index to finish at its highest close in a week.

The benchmark FTSE 100 index gained 0.5% to 6,625.25, and finished up 1% for the week shortened by the Good Friday holiday. Read: The best stocks to play thriving U.K. economy.

Heading into the holiday, stocks had been down as talks between Ukraine, Russia, the European Union and the U.S. were being held in Geneva centered on Ukraine's political crisis and tension with Russia. Russian President Vladimir Putin on Thursday said the Kiev government committed "a serious crime" by sending in troops to stop unrest in Ukraine's eastern region.

Three pro-Russian protesters were killed and 13 wounded on Thursday after a clash with Ukrainian authorities at a military installation in the southeastern city of Mariupol, weighing on markets in Europe early in the trading day.

Later in the day, Barclays (BCS) shares climbed, ending up by 3.8% as the lender, in an internal memo, said it will make changes at its investment bank as it becomes a smaller, more-focused entity to adapt to tougher regulatory and economic conditions. Barclays said in a statement it plans to update the market on May 6.

Royal Bank of Scotland Group PLC (RBS) also rose, by 0.9% after the lender published an independent report dismissing allegations that it systematically tried to defraud struggling business customers and take their assets.

Lloyds Banking Group PLC (LYG) climbed 2% and heavyweight HSBC Holdings PLC (HSBC) put on 0.2%.

On a more downbeat note, Diageo PLC led decliners on the FTSE 100. Shares fell 3.7% after the drinks company, whose brands include Smirnoff vodka and Guinness stout, said sales declined 1.3% in the third quarter, on currency weakness as well as on softer activity in emerging markets.

British luxury-products retailer Mulberry Group PLC warned Thursday it now expects annual profit before tax of roughly GBP14 million ($23.5 million), slightly below expectations. Mulberry said it plans to unveil lower-priced products in a bid to bolster sales. Mulberry shares , which are off of the FTSE 100, dropped 1.1%.

Meanwhile, shares of Burberry Group PLC shed 1.8%. Burberry on Wednesday said second-half sales rose 19%, but that it expects currency exchange rates to weigh on profit.

Although unlisted, investors in U.K. assets keep watch on Co-operative Group Ltd., and the embattled conglomerate posted a full-year net loss of GBP2.3 billion ($3.86 billion), mainly stemming from an operating loss at Co-operative Bank PLC of GBP1.44 billion.

The FTSE 100 finished Thursday's session up by 0.7%.

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