London close: Stocks slide after US jobs disappointment

After an uncertain start following a raft of mixed company updates, London's leading share index finished firmly in the red as some weak US jobs data set nerves on edge. Unemployment claims in the world's biggest economy unexpectedly rose by 5,000 to 417,000 in the week to 20 August. Traders are now looking ahead to the Federal Reserve's annual meeting tomorrow. Here, Kazakhstan-focused copper miner Kazakhmys was in demand after it said underlying profits were 24% ahead in the first half and revealed details of a $250m buy-back programme. The group said the contribution from sector peer ENRC, in which it owns a 26% stake, increased significantly over the year. ENRC, too, was among the best performers in the morning.FTSE 100 drinks giant Diageo was firmer after it posted a 2% increase in sales in the year ended 30 June, as strong growth in the emerging markets outweighed more subdued conditions in Europe.A 12% increase in sales saw FTSE 100 global engineering firm IMI, another big gainer today, top the £1bn revenue mark in the first half, enabling the group to up its dividend by 22%. Shares jumped higher.A strong performance in its mining and power and process divisions, and increased activity in the UK North Sea, more than offset the anticipated reduction in activity levels within the oil sands and federal businesses of AMEC in the first half of 2011, but the shares fell.Banking trioRBS, Barclays and Lloyds were in demand.Car insurer Admiral was a heavy faller, extending losses from Wednesday when the firm disappointed with a worse-than-expected combined ratio.In the FTSE 250, strong demand for gadgets such as smartphones and flat screen TVs helped AZ Electronic Materials, a supplier speciality chemical materials to technological manufacturers, move into profit in the six months to 30 June. The shares were earlier up more than 10%. Pre-tax profits totalled $60.9m for the period, against a loss of $290.8m for the same period the previous year, on revenues that soared to $391.8m from $320.7m. Russian gold miner Petropavlovsk's profits and revenues soared in the half year to 30 June as it benefitted from continuing strong demand for the precious metal as investors seek a haven amid economic uncertainty. The shares moved higher.Turning to the mid-cap fallers, Premier Oil saw profits tumble in the first half of the year but maintained its production estimates. Pre-tax profits came in at £32.5m, down from £111.6m the previous year. Unlike Tullow, which cut its 2011 forecasts on Wednesday, Premier offered no surprises on the operational front, with production just shy of 37,000 barrels of oil equivalents per day (boepd) and full-year guidance maintained at 40-45,000 boed.FTSE 100 - RisersBarclays (BARC) 157.90p +5.55%Royal Bank of Scotland Group (RBS) 23.08p +5.53%Kazakhmys (KAZ) 997.00p +5.17%Diageo (DGE) 1,170.00p +4.65%Lloyds Banking Group (LLOY) 30.99p +2.92%IMI (IMI) 807.50p +2.80%International Power (IPR) 314.90p +2.47%GKN (GKN) 187.80p +2.34%ICAP (IAP) 446.40p +0.97%Burberry Group (BRBY) 1,218.00p +0.66%FTSE 100 - FallersAdmiral Group (ADM) 1,279.00p -5.47%Hargreaves Lansdown (HL.) 404.40p -4.94%Man Group (EMG) 206.10p -4.63%Marks & Spencer Group (MKS) 316.10p -4.44%Amec (AMEC) 876.00p -4.31%BG Group (BG.) 1,218.50p -3.87%Standard Life (SL.) 192.50p -3.65%National Grid (NG.) 589.50p -3.52%Kingfisher (KGF) 223.30p -3.42%G4S (GFS) 262.40p -3.39%FTSE 250 - RisersAZ Electronic Materials SA (WI) (AZEM) 226.90p +7.54%Rightmove (RMV) 1,205.00p +5.70%Persimmon (PSN) 430.50p +5.33%Talvivaara Mining Company (TALV) 320.80p +3.82%Ferrexpo (FXPO) 351.90p +3.81%Phoenix Group Holdings (DI) (PHNX) 541.00p +3.74%Barratt Developments (BDEV) 73.65p +3.66%Kenmare Resources (KMR) 43.50p +3.57%Stagecoach Group (SGC) 250.10p +3.39%Taylor Wimpey (TW.) 30.50p +3.32%FTSE 250 - FallersPremier Oil (PMO) 316.00p -9.71%Computacenter (CCC) 354.80p -6.39%Britvic (BVIC) 289.90p -6.27%SIG (SHI) 100.00p -6.10%RIT Capital Partners (RCP) 1,212.00p -4.57%Pace (PIC) 99.60p -4.32%Afren (AFR) 95.20p -4.08%Exillon Energy (EXI) 285.00p -4.07%Mitchells & Butlers (MAB) 226.60p -3.94%Catlin Group Ltd. (CGL) 351.40p -3.70%