UK's FTSE falls as Swiss central bank unnerves stock markets

* European stock markets hit by Swiss central bank move

* Swiss National Bank scraps euro/franc cap

* FTSE 100 down 0.6 pct

* Glaxo and Astra pressured by drop in Swiss rival Roche

By Sudip Kar-Gupta

LONDON, Jan 15 (Reuters) - Britain's top equity index fell on Thursday after the Swiss National Bank (SNB) unexpectedly scrapped its cap on the euro value of the franc, hitting blue-chip stocks across Europe.

The FTSE 100 index fell 0.6 percent to 6,349.52 points, the franc soared and Swiss stocks fell on fears that demand for Swiss exports would dive. Dealers said the SNB's decision had unnerved investors as it raised the possibility of future unexpected moves by other central banks.

"It's not every day that a central bank pulls the rug out from underneath something in such a massive way, and clearly people are worried that there's something bigger afoot. This kind of event is the kind of thing that will trigger volatility. This is not a one-day thing now," said IG (LSE: IGG.L - news) market analyst Chris Beauchamp.

UK drugmakers GlaxoSmithKline (Other OTC: GLAXF - news) and AstraZeneca (Swiss: AZN.SW - news) both fell by more than 1 percent, hit by a slump at Swiss rival Roche.

"Major losses in euro-franc trades are causing panic selling and deleveraging across the board," said Hampstead Capital LLP hedge fund manager Lex Van Dam.

Further weakness in oil prices hit energy stocks such as Tullow Oil (LSE: TLW.L - news) . The company announced a $2.3 billion write-off and reduced its 2015 investment programme as a result of the decline in the oil price to near six-year lows. (Additional reporting by Francesco Canepa; Editing by Louise Ireland (Other OTC: IRLD - news) )