* FTSE 100 and FTSE 350 indexes both up 0.7 percent
* TSB up 23 pct after receiving takeover bid
By Atul Prakash and Francesco Canepa
LONDON, March 12 (Reuters) - UK shares rose on Thursday, led by domestic bank TSB after it received a takeover offer, and by drugs group AstraZeneca on optimism about key trial results.
Shares in TSB, which was spun off from Lloyds and listed at 280 pence per share last year, rose 23 percent to 326 pence as it received a takeover bid from Spain's Sabadell for 340 pence.
"This more or less looks like a done deal," said Beaufort Securities sales trader Basil Petrides.
The stock was the top riser on the FTSE 350 index of UK shares, which was up 0.7 percent at 3,724.17 points at 1517 GMT.
The blue-chip FTSE 100 index was also up 0.7 percent, at 6,771.24 points. The index is up about 3 percent so far this year.
AstraZeneca topped FTSE 100 risers as it surged 3.9 percent on the back of hopes for positive news on its key heart drug Brilinta when full clinical trial results are presented at weekend.
"The study should be a major driver for treatment duration, and thus should finally unlock Brilinta's multi-billion dollar potential," analysts at UBS wrote in a note on Thursday, giving the shares a buy rating.
Among mid-cap firms, oil producer Soco International slumped 30 percent after reporting a 54 percent fall in profits last year on the back of weak oil prices.
Another mid-cap firm Serco dropped 12.5 percent after kicking off a 555 million pound ($831 million) rights issue and saying it was unlikely to return to growth for another three years, as it reported a collapse in profits.
Several FTSE 100 companies fell after trading without the attraction of their latest dividend payouts. According to Reuters calculations, the effect of the resulting adjustment to prices by market-makers took 8.24 points off the index. (Additional reporting by Sudip Kar-Gupta; Editing by Andrew Heavens)