Britain's Steve Cummings, another member of the breakaway, finished an impressive fourth on a long day that took in three punishing climbs.
Danilo di Luca (LPR) and Riccardo Ricco (Saunier Duval) both put significant time into Alberto Contador, though the Astana man managed to cling onto his pink jersey by just four seconds.
A seven man group comprised of Kiryienka (Tinkoff), Cummings (Barloword), Giairo Ermeti (LPR), Alexandre Efimkin (Quickstep), Nicki Sorensen (CSC) , Kanstantin Siutsou (High Road) and Gabriele Missaglia (Diquigiovanni) took advantage of a slight drop in pace after a fast first hour of racing to jump clear of the peloton.
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They rode out a lead that grew to over 20 minutes on the ascent of the first climb of the day, the Passo del Vivione, as the heavens opened and the rain came teeming down.
Spotting an opportunity for an attack, di Luca jumped on Paolo Savoldelli's tail on the descent, with the latter showing just why is nicknamed “the falcon,” and leading his team-mate down the technical, rain-soaked descent at breakneck speed. Liquigas' Vincenzo Nibali managed to cling on to their coat-tails as the trio built up a lead of over a minute by the time they reached the second climb of the day, the Passo della Presolana.
Andreas Klöden moved to the front for Astana, and managed to eat into Di Luca's lead marginally on the Presolana, while Gilberto Simoni (Diquigiovanni) was dropped.
Meanwhile, the breakaway out front was beginning to fragment, with Kiryienka putting in an attack that saw Siutsou and Sorensen fall away immediately, while Efimkin and Cummings strived in vain to keep the Russian in their sights.
By the foot of the final climb, the Monte Pora, Savoldelli had ridden himself into the ground for Di Luca, and Klöden had done likewise further back down the road for Contador. Both moved aside as the captains were left to fend for themselves.
Ricco, who had been looking ominously comfortable all day, then put in a burst that Contador was unable to match, and then went all out in pursuit of the race lead.
He gradually moved away from Contador's group, while Kiryienka crossed the line victorious, and Di Luca successfully chased down both Cumminga and Efimkin from the breakaway to take second place on the stage an earn a valuable 12-second time bonus.
Ricco came home a minute behind Di Luca, with Contador almost a further minute back still. The Spaniard crossed the line at the back of his group, pain etched on his face.
His efforts were enough to see him preserve his pink jersey, though Ricco now lies just four seconds behind on the general classification, with Di Luca 21 seconds back. Not to be discounted is Marzio Bruseghin (Lampre), who finished safely in the Contador group, and still lies 2'00” back on the GC. If he was hitherto viewing the final time-trial as an opportunity for a stage win, he might now be looking at it as a chance to grab his first ever grand tour victory.
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