* FTSEurofirst 300 up 0.4 pct, Euro STOXX 50 up 0.5 pct
* AstraZeneca stock jumps 15 pct as Pfizer says to buy firm
* Bayer rallies after posting forecast-beating results
PARIS, April 28 (Reuters) - European stocks rose on Monday, as gains in the pharma sector driven by merger moves and forecast-beating results from Germany's Bayer outweighed the impact of tensions in Ukraine.
Shares in AstraZeneca surged 15 percent after U.S. rival Pfizer said it wanted to buy the British drugmaker in a deal potentially worth more than $100 billion.
The sharp jump in the stock represented a rise in the group's market capitalisation of roughly 7.7 billion pounds, or $13 billion.
Shares in German conglomerate Siemens dropped 2.3 percent after the group said it was mulling an asset swap with France's Alstom, which has received an offer for its power arm from U.S. bellwether General Electric.
"Thanks to central banks' massive (provision of) liquidity, a lot of companies are now looking for takeover targets across the board, which is very positive for the market," said Lionel Jardin, head of institutional sales at Assya Capital, in Paris.
"It helps forget about Ukraine, which seems to slowly disappear from investors' radar screens despite the violence. With time, investors are getting used to the crisis."
At 0807 GMT, the pan-European FTSEurofirst 300 index , which hit a near six-year high earlier this month, was up 0.4 percent at 1,337.39 points.
The index lost 0.8 percent on Friday as investors moved to the sidelines, wary of a potential deterioration in the Ukrainian crisis over the weekend.
President Barack Obama on Sunday called for the United States and Europe to join forces to impose stronger measures to restrain Moscow. In a move senior U.S. officials said may come as early as Monday, the White House said it would add names of people close to President Vladimir Putin and firms they control to a list of Russians hit by sanctions over Ukraine, and also impose new restrictions on high-tech exports.
On the earnings front, shares in Bayer gained 3.8 percent after posting forecast-beating quarterly results, helping Germany's DAX outperform.
Frankfurt's benchmark index was up 0.5 percent. The UK's FTSE 100 index was up 0.3 percent and France's CAC 40 up 0.4 percent.
"Indexes are still stuck in ranges for now. The dip buyers are offsetting the selling pressure, and the longer-term trend is still positive," Aurel BGC chartist Gerard Sagnier said.
Despite Bayer, the overall earnings picture for Europe remains mixed.
About one-fifth of companies of the STOXX Europe 600 index have reported quarterly results so far, of which half have beaten or met analysts' expectations. Some 75 percent of U.S. companies have beaten or met forecasts.
Europe bourses in 2014: link.reuters.com/pap87v
Asset performance in 2014: link.reuters.com/gap87v
Today's European research round-up (additional reporting by Atul Prakash in London; Editing by John Stonestreet)