* FTSEurofirst 300 down 0.5 pct
* Tech sector weaker with Gemalto also sliding
* Portugal Telecom drops as Rioforte set for liquidation
* Nutreco, Adidas, Havas surge on M&A activity (Updates prices, adds quote, detail)
By Alistair Smout
EDINBURGH, Oct 20 (Reuters) - European stocks fell on Monday, trimming lofty gains made in the previous session, with SAP's profit warning hitting shares in the tech sector.
Shares in the German business software maker plunged 6.6 percent after it cut its outlook for full-year operating profit, joining a succession of profit and sales warnings from tech groups in the past few weeks.
Dutch tech firm Gemalto fell 3.2 percent after Barclays cut the stock to underweight from overweight, joining SAP as a top faller on the STOXX 600 Technology index, which was down 2.8 percent.
SAP was the worst performer on the German DAX, which fell 1.6 percent, lagging other major European stock indexes. It has dropped around 8 percent so far in October, after data called into question Germany's economic resilience.
Both the technology sector and German blue-chip index are very sensitive to economic growth, or highly "cyclical".
"It's all about growth at the moment. Cyclicals have been underperforming in recent months ... (and) with respect to SAP, it's a result of the business investment climate," Mike Ingram, market strategist at BGC Partners, said.
"People don't think that the broad-based acceleration in global economic growth, expected at the start of the year, is going to pan out." He saw the DAX's high exposure to growth-sensitive stocks keeping it under pressure.
Outside the FTSEurofirst 300 of top European shares, Portugal Telecom fell 15.2 percent on worries that it would have to write off debt as Portugal's Rioforte headed towards liquidation.
At 1423 GMT, the FTSEurofirst 300 was down 0.5 percent at 1,273.33 points, trimming Friday's 2.8 percent rise prompted by reassuring U.S. macroeconomic data.
"We're seeing this as a buying opportunity. The German market looks cheap having lagged so far this year," James Butterfill, global equity strategist at Coutts, said.
"We don't think the fundamental data points to a recession, which is what the market has been pricing in."
Shares in Electrolux jumped 7.1 percent after the home appliances maker reported forecast-beating quarterly profits.
The market's losses were also limited by brisk M&A activity, boosting the shares of Nutreco, Adidas and Havas.
Shares in Dutch animal feed and nutrition company Nutreco soared 39 percent after a Dutch investment firm said it had agreed to acquire the group.
German sportswear firm Adidas AG surged 4.6 percent after the Wall Street Journal reported that an investor group was planning a bid to buy Adidas's Reebok unit.
Havas also rose, by 3 percent, after French tycoon Vincent Bollore launched an exchange offer on the stock on Friday with a view to gaining control of the world's sixth-largest advertising company. Shares in Groupe Bollore dropped 10.7 percent.
Europe bourses in 2014: link.reuters.com/pap87v
Asset performance in 2014: link.reuters.com/gap87v
Today's European research round-up (Editing by Ruth Pitchford)