UPDATE 1-Tennis-Murray reaches last eight, Safin and Youzhny out

(Adds Youzhny defeat, more quotes)

ST PETERSBURG, Oct 23 (Reuters) - Top seed Andy Murray raced into the quarter-finals of the St Petersburg Open with a 6-4 6-2 win over Latvian Ernests Gulbis on Thursday.

The in-form Briton, fresh from winning the Madrid Masters on Sunday, put an assured display against the 50th-ranked Gulbis, securing a key break in the eighth game to take the first set.

Murray, who won here last year on his debut appearance in Russia's second city, then breezed through the second to complete a comfortable victory in just over an hour and stay on course for his second title in two weeks.

The world number four, who dismissed Serbian Viktor Troicki in straight sets in the first round on Wednesday, next faces his compatriot Janko Tipsarevic, a 6-4 7-6 winner over Frenchman Jeremy Chardy.

Earlier, former world number one Marat Safin, the eighth seed, slumped to a 6-4 6-2 defeat by Kazakh qualifier Andrey Golubev.

The big Russian, who won here in 2000 and 2001, was outhit and outplayed by the 150th-ranked Golubev.

The slightly-built Kazakh, who has played mainly on a Challenger circuit and has won only three ATP matches in his career until this week, also fired more aces, seven to Safin's five.

"He (Golubev) totally deserved his victory," Safin told reporters. "He served better than me, was more consistent from the baseline and made less mistakes."