Romain Grosjean cut Giorgio Pantano's GP2 championship lead to five points after winning an incident-filled race two in Istanbul that saw Bruno Senna forced to retire after htting a stray dog.

Britons Mike Conway and Ben Hanley collected their first points of the season with fifth and sixth place respectively.

Grosjean claimed his first win of the year after pressuring early leader Vitaly Petrov throughout the first half of the race, taking the lead in the latter stages for a dominant victory ahead of Petrov and Sébastien Buemi.

While the Frenchman celebrated, sympathy from the pitlane was with Senna, who drove impressively to move up from 15th on the grid only to see a certain points finish disappear when he struck a dog that had strayed onto the track.

The incident broke Senna's right front suspension and forced the nephew of Formula One legend Ayrton to retire while running in sixth place.

Petrov made a storming start from fourth to claim top spot into the first turn, while Grosjean pushed Karun Chandhok into polesitter Adam Carroll, allowing Buemi and Javier Villa to line up behind the Russian but ahead of the Frenchman as they tore up the hill.

Behind them mayhem ensued, with eight drivers out on the spot and the safety car immediately called.

At the restart, Grosjean wasted little time getting by Villa, who was also passed by team-mate Pantano a few corners later.

The order was shaking out all through the field as the drivers attacked all over the circuit, although Chandhok and Villa took it too far and the inevitable contact put them into spins which ended their chances of picking up points.

Senna, in particular, looked unstoppable as he set a string of fastest laps to move up into the points positions. The Brazilian struck the dog coming into the final complex and he limped back to the pits before storming off, clearly fuming.

One lap later Grosjean's race-long pressure finally paid dividends as he slid inside Petrov at the end of the back straight to claim a lead which he never looked like relinquishing.

When another dog ran on track the safety car returned, again compacting the field for the final run to the flag. But Grosjean was imperious at the restart, while Petrov's mirrors were full of Buemi's Arden for the remainder of the race.

While the order further back was still changing by the lap, up front the top three were followed across the line by Pantano, Conway and Hanley, the two Britons rewarded for staying out of trouble.

Pantano's fourth place was enough to maintain his Championship lead and set up an intriguing battle in Monaco.

Pantano leads with 24 points, Grosjean lies second with 19, ahead of Buemi on 14 and Andreas Zuber with 13.

Racing Engineering leads the teams' championship ahead of ART Grand Prix, Trust Team Arden and iSport International.

From Official Website