Decent gains from banking and supermarket stocks helped the FTSE 100 rise on Thursday, as investors showed optimism about continuing talks between Greece and its creditors.RBS was among the best performers in London after the government announced plans to sell down its stake, while Sainsbury's was leading grocers higher after a broker upgrade.The FTSE 100 was up 0.2% at 6,844.21 by midday.Stocks across Europe were also rising with equities in Greece on track for their biggest leap since February after Greek prime minister Alexis Tsipras and leaders in Germany and France agreed to intensify talks. The Athens Stock Exchange was up 7% by lunchtime."The European leaders realised that we must offer a viable solution and the chance for Greece to return to growth," he said, following talks with Angela Merkel and Francois Hollande. He said that a deal "must bring sustainable debt, and a perspective that will provide security and stability not only to Greece, but also to Europe"."Traders are still wary about buying into the market but there are bargains to be had, and the smallest inclination of a deal being made has brought the bulls out of the woodwork," said analyst David Madden from IG.Improving economic data from China also helped to improve sentiment in the market as figures showed the annual growth rate of industrial production and retail sales picked up in May.RBS and Sainsbury's gainGeorge Osborne has announced the government will begin the process of returning RBS to private ownership in the "coming months," even though it may cause a loss for taxpayers. Spreadex analyst Connor Campbell said "investors in the stock are clearly pleased by the news".Lloyds and Barclays were also in demand.J Sainsbury was a high riser after Cantor Fitzgerald upgraded the stock to 'buy' from 'hold', saying it believes the industry is near the bottom of its current deflation and margin cycle.Tesco and Morrisons were also performing well.Heading the other way was Royal Mail after the government offloaded half of its stake in the postal operator for £750m. The stock pulled back after PostNL announced the suspension of Whistl's UK direct delivery operations.Vodafone was also on the decline after Ofcom said it was investigating the telecoms giant relating to billing and customer complaint handling. Market MoverstechMARK 3,215.26 +0.06%FTSE 100 6,844.21 +0.20%FTSE 250 18,103.61 +0.41%FTSE 100 - RisersSainsbury (J) (SBRY) 266.80p +2.50%Tesco (TSCO) 216.35p +2.32%Royal Bank of Scotland Group (RBS) 361.40p +1.86%CRH (CRH) 1,872.00p +1.63%Morrison (Wm) Supermarkets (MRW) 182.60p +1.50%Kingfisher (KGF) 384.60p +1.37%British Land Company (BLND) 840.00p +1.08%Aviva (AV.) 521.00p +1.07%St James's Place (STJ) 894.50p +1.07%Burberry Group (BRBY) 1,684.00p +1.02%FTSE 100 - FallersRoyal Mail (RMG) 498.30p -3.52%Vodafone Group (VOD) 235.95p -3.34%Standard Chartered (STAN) 1,073.50p -1.87%Johnson Matthey (JMAT) 3,188.00p -1.82%Fresnillo (FRES) 727.50p -1.36%Antofagasta (ANTO) 726.50p -1.29%United Utilities Group (UU.) 962.00p -0.82%easyJet (EZJ) 1,577.00p -0.82%Reckitt Benckiser Group (RB.) 5,707.00p -0.57%Glencore (GLEN) 278.80p -0.54%FTSE 250 - RisersNostrum Oil & Gas (NOG) 554.00p +4.33%Vedanta Resources (VED) 615.50p +3.19%Mitchells & Butlers (MAB) 466.50p +3.05%Crest Nicholson Holdings (CRST) 561.50p +2.74%Spire Healthcare Group (SPI) 357.50p +2.73%Just Retirement Group (JRG) 177.50p +2.72%Grainger (GRI) 217.20p +2.60%Cairn Energy (CNE) 189.50p +2.38%Jardine Lloyd Thompson Group (JLT) 1,042.00p +2.26%Aveva Group (AVV) 1,980.00p +2.22%FTSE 250 - FallersCineworld Group (CINE) 472.10p -3.10%Acacia Mining (ACA) 298.70p -3.08%Evraz (EVR) 159.10p -2.69%Intermediate Capital Group (ICP) 566.00p -2.25%FirstGroup (FGP) 124.50p -1.89%LondonMetric Property (LMP) 165.00p -1.79%Petra Diamonds Ltd.(DI) (PDL) 168.40p -1.58%Booker Group (BOK) 180.50p -1.53%Kaz Minerals (KAZ) 250.10p -1.34%Inmarsat (ISAT) 970.50p -1.22%