- China's Wen dampens sentiment- Miners drop on Chinese worries, Nomura comments- G4S tumbles on Olympics contract loss estimatesLondon's benchmark index opened slightly lower on Monday morning as comments from China's Premier weighed heavily on stocks in the mining sector. G4S also took a tumble early on after revealing estimated losses for its Olympics contract.After China registered its sixth straight quarterly slowdown in growth last week, Premier Wen Jiabao had some worrying words about his country's economy as he noted that the expected rebound was still not as stable as forecast. "It should be clearly understood that the momentum for a stable rebound in the economy has not yet been established," he warned according to a report from the state-run Xinhua news agency.Meanwhile, analyst Craig Erlam said that the US Federal Reserve (Fed) and its Chairman Ben Bernanke will be in the spotlight again this week ahead of the semi-annual monetary policy report on Tuesday and Wednesday. "With the testimony completely unscripted, people will play close attention for any indication that the Fed will loosen the purse strings in the second half of the year. Given recent testimonies and comments from the Fed Chairman, I expect we'll see more of the same comments again," he said.Miners, G4S and National Grid provide a dragRandgold Resources, Rio Tinto, Polymetal, Fresnillo and ENRC were heavy fallers on the back of Wen's comments and concerns over a slowdown in the world's second-largest economy. Also weighing on stocks was Nomura which lowered its price targets across the mining sector after cutting its commodity price forecasts. Sector peer Glencore International was falling by a lesser rate after announcing that the acquisition of agricultural business Viterra has been approved by Canadian authorities.British luxury brand Burberry, a stock sensitive to developments in the Chinese economic outlook (a key growth market for the business) was also out of favour early on.Nevertheless, it was security solutions firm G4S dropped nearly 9% after saying that it will incur a loss on its Olympics Games contract of £35-50m after failing to provide the number of staff for the event that it had committed to. Chief Executive Officer Nick Buckles said: "We are deeply disappointed that we have not been able to fully deliver against our contract with LOCOG and that it has been necessary to call upon the additional military personnel."National Grid, Britain's biggest distributor of gas and electricity, was lower after Ofgem's plans for the upgrade of the UK's power network. The firm says the initial plans, which envisage up to £22bn of investment between 2013 and 2021, "differ substantially" from its own business plan. Smiths Group, the technology company, was higher after saying that it is selling its share of US biometric firm Cross Match Technologies. Accountancy software leviathan Sage said it was still waiting for the looked-for pick-up in Europe to happen, causing shares to fall. However, Sage assured that it has been trading broadly in line with expectations since the end of March.Elsewhere, AIM-listed oil and gas group Borders & Southern plummeted after saying that it has been forced to plug and abandon its Stebbing well after being unable to reach all its potential reservoir targets due to "anomalous pressure conditions".FTSE 100 - RisersSmiths Group (SMIN) 1,060.00p +2.22%Resolution Ltd. (RSL) 216.90p +2.12%Schroders (SDR) 1,330.00p +1.22%International Consolidated Airlines Group SA (CDI) (IAG) 157.20p +0.90%Vodafone Group (VOD) 184.50p +0.90%British Land Co (BLND) 529.50p +0.76%CRH (CRH) 1,200.00p +0.76%GlaxoSmithKline (GSK) 1,454.00p +0.55%ICAP (IAP) 311.50p +0.52%Imperial Tobacco Group (IMT) 2,553.00p +0.51%FTSE 100 - FallersG4S (GFS) 254.50p -8.68%Burberry Group (BRBY) 1,200.00p -2.36%Randgold Resources Ltd. (RRS) 5,785.00p -2.36%National Grid (NG.) 678.00p -2.16%Sage Group (SGE) 278.90p -2.14%British Sky Broadcasting Group (BSY) 680.00p -2.02%Rio Tinto (RIO) 2,963.00p -1.89%Polymetal International (POLY) 862.50p -1.65%Kazakhmys (KAZ) 732.00p -1.61%Evraz (EVR) 250.70p -1.57%FTSE 250 - RisersDaejan Holdings (DJAN) 2,970.00p +3.59%Computacenter (CCC) 313.90p +2.68%Britvic (BVIC) 280.00p +2.53%Salamander Energy (SMDR) 183.40p +2.40%Phoenix Group Holdings (DI) (PHNX) 502.00p +1.91%PZ Cussons (PZC) 319.90p +1.62%Petra Diamonds Ltd.(DI) (PDL) 127.10p +1.52%Dunelm Group (DNLM) 563.00p +1.44%Close Brothers Group (CBG) 777.00p +1.37%Hays (HAS) 67.80p +1.19%FTSE 250 - FallersPerform Group (PER) 384.10p -5.16%Bumi (BUMI) 297.80p -3.94%Ocado Group (OCDO) 70.45p -3.69%Petropavlovsk (POG) 445.00p -3.60%Kentz Corporation Ltd. (KENZ) 375.00p -3.00%Moneysupermarket.com Group (MONY) 131.40p -2.67%Home Retail Group (HOME) 79.90p -2.32%Kenmare Resources (KMR) 33.00p -2.11%Menzies(John) (MNZS) 593.50p -2.06%TR Property Inv Trust (TRY) 153.00p -1.61%BC