** Shares of engineering contractor Keller Group KLR.L up as much as 20% at 1,570p
** Stock is among top pct gainers on FTSE Midcap .FTMC index
** Company reports 30% rise in preliminary FY underlying diluted EPS of 199.9p, driven by lower financing costs, reduced tax rate
** Expects to launch multi-year share buyback programme, with initial tranche of 25 mln pounds ($31.79 mln) in Q1
** KLR expects 10% increase to its FY dividend
** Stock has lost ~11% YTD
($1 = 0.7863 pounds)
(Reporting by Anandita Mehrotra in Bengaluru)
((Anandita.Mehrotra@thomsonreuters.com))