- Gaza fighting, Ukraine crisis continues to dampen risk appetite- UK house prices fall for first time this year- Tobacco stocks hit by major fine for US peer- Tesco issues profit warning as CEO resignstechMARK 2,796.34 -0.27%FTSE 100 6,726.20 -0.34%FTSE 250 15,467.80 -0.57%Geopolitical concerns were continuing to dominate the direction on Monday with UK stocks firmly lower by midday on the back of ongoing fighting in Gaza and the fallout from the Malaysia Airlines crash in Ukraine last week.Data showing the first fall in UK house prices this year was dampening a number of housing and construction stocks in London, while tobacco stocks were lower on the news of a major fine imposed on US group RJ Reynolds. Meanwhile, Tesco was rising as investors welcomed the departure of its boss.The FTSE 100 was down 0.3% at 6,726 by around noon.Chris Beauchamp, Market Analyst at IG, said that there has been "an outbreak of risk aversion" this morning in the UK equity market."Amidst all the noise and contrary signals traders will have their work cut out for them to establish a clear picture, as shown by the sharp drop and equally sharp bounceback on the final two days of last week," he said.Gaza, UkraineOver the weekend, calls came from the UN Security Council for a ceasefire between Israeli and Palestinian forces, which are currently engaged in a deadly battle in Gaza. Over 500 Palestinians have now been killed, with Sunday being the deadliest day since fighting began just two weeks ago.Meanwhile, UK Prime Minister David Cameron has signalled his support for additional sanctions to be made against Russia, and will today inform MPs about the steps being taken to gain "unfettered access" to the crash site in Ukraine. US Secretary of State John Kerry has also demanded that Russia take responsibility.Tensions between Russia and Ukraine have escalated as the two nations pointed blame towards each other over the downing of a Malaysia Airlines plane in Ukraine on Thursday which killed all 298 people on board. The UN Security Council will today vote on a resolution to make sure those responsible are held accountable.Tesco rises despite profit warning as Clarke quitsRetail giant Tesco this morning unveiled a profit warning after a "challenging" second quarter, but shares gained after investors welcomed the resignation of its boss Philip Clarke. Clarke "agreed [...] that this is the appropriate moment to hand over to a new leader with fresh perspectives and a new profile", the company said, and will be replaced by Unilever exec Dave Lewis.Tesco's supermarket rivals Wm Morrison and J Sainsbury were both lower.Housing stocks fell after Rightmove data showed that the average asking price for a UK home dropped 0.8% from £272,275 in June to £270,159 in July. Barratt Developments, Persimmon and Bovis Homes were all in the red by midday.British American Tobacco (BAT) and Imperial Tobacco dropped after RJ Reynolds was told to pay the widow of a cancer victim $23.6bn in damages amid claims that the company was negligent in informing the public about the dangers of smoking. RJ Reynolds is wholly owned by Reynolds American, which is 42% owned by BAT.Engineering support services group Babcock was in demand after saying that the new financial year "has started well" with activity levels remaining high.Media firm BSkyB fell as it announced the purchase of a 70% stake in UK production group Love Productions, which makes programmes such as the Great British Bake-Off. BSkyB continues to be dominated by speculation that it will buy the Italian and German pay-TV assets from 21st Century Fox.FTSE 100 - RisersTesco (TSCO) 291.30p +2.21%Severn Trent (SVT) 1,948.00p +1.14%Randgold Resources Ltd. (RRS) 5,115.00p +0.99%BAE Systems (BA.) 421.30p +0.98%Antofagasta (ANTO) 813.00p +0.93%Anglo American (AAL) 1,551.00p +0.91%Babcock International Group (BAB) 1,110.00p +0.91%AstraZeneca (AZN) 4,366.50p +0.61%Smiths Group (SMIN) 1,231.00p +0.57%Fresnillo (FRES) 906.00p +0.55%FTSE 100 - FallersMorrison (Wm) Supermarkets (MRW) 173.60p -2.47%Barratt Developments (BDEV) 356.90p -1.84%Petrofac Ltd. (PFC) 1,171.00p -1.76%British Sky Broadcasting Group (BSY) 902.00p -1.69%TUI Travel (TT.) 366.00p -1.64%Imperial Tobacco Group (IMT) 2,645.00p -1.56%Pearson (PSON) 1,111.00p -1.51%Sainsbury (J) (SBRY) 320.00p -1.45%Coca-Cola HBC AG (CDI) (CCH) 1,381.00p -1.43%Hargreaves Lansdown (HL.) 1,086.00p -1.36%FTSE 250 - RisersEntertainment One Limited (ETO) 332.60p +2.78%Hochschild Mining (HOC) 164.80p +2.74%Just Eat (JE.) 220.00p +2.61%Galliford Try (GFRD) 1,271.00p +2.25%Centamin (DI) (CEY) 73.45p +1.94%Poundland Group (PLND) 323.40p +1.47%Telecity Group (TCY) 766.00p +1.46%Soco International (SIA) 409.00p +1.44%Petra Diamonds Ltd.(DI) (PDL) 206.80p +1.22%Pets at Home Group (PETS) 185.20p +1.20%FTSE 250 - FallersITE Group (ITE) 206.50p -3.95%Euromoney Institutional Investor (ERM) 1,058.00p -2.94%COLT Group SA (COLT) 131.30p -2.74%Greencore Group (GNC) 272.40p -2.51%FirstGroup (FGP) 129.40p -2.34%Inmarsat (ISAT) 753.00p -2.33%Evraz (EVR) 99.10p -2.17%Restaurant Group (RTN) 573.00p -2.13%Just Retirement Group (JRG) 139.90p -2.03%Cineworld Group (CINE) 318.30p -2.03%BC