Nadal, Federer and Murray through to quarter-finals

DOHA (Reuters) - Top three seeds Rafael Nadal, Roger Federer and Andy Murray continued their serene progress at the Qatar Open on Wednesday, reaching the quarter-finals with straight-sets victories.

World number one Nadal outplayed Slovakia's Karol Beck 6-1 6-2, Federer beat Italy's Andreas Seppi 6-3 6-3 and Murray knocked out Germany's Philipp Petzschner 6-2 6-4.

Fourth seed Andy Roddick also made it safely through, with a slightly less convincing 6-3 7-5 victory over French wild card Arnaud Clement.

Nadal took just over an hour to see off qualifier Beck, reeling off six straight games after falling behind 0-2 in the second.

"Although I lost my concentration for a while in the second set, I really played well today," said Nadal, who had a similarly easy win over Fabrice Santoro on Tuesday.

Nadal will take on French wild card and fifth seed Gael Monfils in the quarter-finals. Monfils, runner-up to Federer in Doha in 2006, fired nine aces as he got the better of compatriot Nicolas Devilder 7-5 7-6, taking the tie-break 7-4.

Federer hit too many unforced errors against Seppi but his victory was never in doubt.

"There were more rallies (than in my first match) and points were not coming easily, even on my own serve," Federer said. "But it was a good match to get my rhythm back."

Federer will meet Philipp Kohlschreiber in the last eight after the German edged out Belgium's Kristof Vliegen 6-4 6-7 6-4.

(Editing by Kevin Fylan)