By Sara Sjolin, MarketWatch

LONDON (MarketWatch) -- U.K.'s benchmark stock index was on track for its best daily performance in almost two months on Thursday, with shares of Rolls-Royce leading the pack after news of a 1-billion-pound share buyback.

The FTSE 100 index climbed 0.8% to 6,829.73, setting it on track for the largest one-day percentage gain since late April.

Rolls-Royce Holdings PLC leapt 6.3% after the engine maker announced a GBP1 billion ($1.7 billion) stock-buyback program and ruled out any major takeovers.

Miners also gained as metals prices were boosted by a weaker dollar. The greenback lost ground on Wednesday after U.S. Federal Reserve Chairwoman Janet Yellen signaled the central bank is in no hurry to raise interest rates, saying there could be "considerable time" between when the bond taper ends and hikes begin. On Thursday, the dollar continued to weaken, with the ICE dollar index (DXY) down to 80.16 from 80.38 late Wednesday.

Shares of Anglo American PLC gained 1.8%, BHP Billiton PLC (BHP) added 1.7%, Antofagasta PLC picked up 1.5% and Rio Tinto PLC (RIO) advanced 1%.

Oil firms were also higher as oil futures edged higher amid continued concern over violence in Iraq. Royal Dutch Shell PLC (RDSB) put on 0.8% and BP PLC (BP) gained 0.5%.

Retailers were further in focus in London after the Office for National Statistics said sales fell 0.5% on the month in May and rose 3.9% compared with May 2013. Sales related the World Cup in Brazil rose 2.2% on the month in May, helping limit the overall drop.

Chris Williamson, chief economist for Markit, said in a note that despite the decline in May, retail sales are still growing at an impressive pace so far this year.

"With sales up some 4.3% on last year during the first five months of 2014, retailers [are] enjoying the best start to a year for a decade," he said.

Shares of do-it-yourself retailer Kingfisher PLC moved 1.3% higher and Next PLC added 0.6%.

More must-reads from MarketWatch:

Janet Yellen's no more confident than the rest of us

How to invest like a rich guy

Identity issue keeps Chicago woman from getting Obamacare plan

Subscribe to WSJ: http://online.wsj.com?mod=djnwires