* FTSEurofirst 300 and Euro STOXX 50 fall back
* Air Liquide down after announcing Airgas deal
* Global security still in spotlight after Paris attacks (Adds details and quote, updates prices)
By Sudip Kar-Gupta and Kit Rees
LONDON, Nov 18 (Reuters) - European shares fell on Wednesday, retreating from solid gains in the previous session, with industrial gas company Air Liquide slipping after announcing an expensive-looking acquisition.
There appeared to be limited market reaction to news that two suspects had died during a police raid in Paris in the wake of last week's attacks. Some European travel and leisure stocks lost ground but they were in line with the overall European market.
"The indices are treading water today ... there seems to be a little bit of trepidation at the moment because of what's been going on in Paris this morning and overnight," said Augustin Eden, research analyst at Accendo Markets.
The pan-European FTSEurofirst 300 index, which rose 2.6 percent in the previous session, fell 0.3 percent while the euro zone's blue-chip Euro STOXX 50 index declined by 0.6 percent.
Air Liquide dropped 6.5 percent after the company announced a $13.4 billion deal to buy U.S. peer Airgas.
"The share price goes down, because investors get spooked by the prospect of a lot of money leaving the company's bank account," said Accendo Markets' Eden.
In a research note, UBS kept a "sell" rating on Air Liquide's shares and described the Airgas deal as "pricey", with Air Liquide's offer price representing a premium of 50.6 percent to Airgas's one-month average share price.
The European travel and leisure sector was down 0.6 percent.
An international soccer match was called off in Germany on Tuesday after a security alert and two Air France flights from the United States were diverted. Air France KLM shares were down 0.4 percent on Wednesday.
Traders pointed to a rally in Russia-exposed stocks after Russia and France conducted air strikes in Syria.
Russia's President Vladimir Putin and France's President Francois Hollande are to meet in Moscow next week, with investors hopeful that a thaw in relations between the West and Russia might mean that sanctions are lifted.
Retailer Metro was up 3 percent, while pharmaceutical company Stada rose 2.3 percent.
Nearly all the companies on the pan-European STOXX 600 index have reported their third-quarter results, with 51 percent beating or meeting market expectations, while 49 percent missed market forecasts.
Expectations for more monetary stimulus from the European Central Bank next month has led some investors to expect further gains for European stocks and the FTSEurofirst is still up nearly 10 percent since the start of 2015.
McLaren Securities' managing director Terry Torrison said his clients had mixed views on European shares in the near term.
"It's a mixed bag. Some are willing to buy into the market, but others think any ECB-led rally will be short-lived as the underlying European economy still has signs of weakness," he said.
Today's European research round-up (Editing by Andrew Roche)