DOHA (AFP) - Venus Williams, who won the Women's Tennis Association (WTA) season-end championships here six years ago, made a winning start to the Qatar Open which brought back great memories at a familiar venue.

The 33-year-old seven-time Grand Slam winner overcame both a blustery wind and Petra Martic, only the second Croatian woman to reach the last 16 of a Grand Slam event, 6-2, 6-2.

Williams struck 15 clean winners with her uncompromising ground strokes, and although she did not land her first serve as frequently as she might have liked, often advanced threateningly to the forecourt, scoring ten times with volleys.

"It's windy and, you know, it's winter in the desert, and the weather can be a little up in the air, so I was just happy to keep the errors down," said Williams who believes that if she can do that regularly she will still beat top level players.

"Unforced errors are always a key for me. Keeping them down makes my life easier. The matches are cleaner, and it helps me win in straight sets.

"So that's my goal this week," added Williams, who has been hampered by fitness issues in the two years since she was last in the world's top 20.

Williams won the first four games in double quick time, and after Martic launched a mini-revival, took the first set with renewed momentum. She maintained it in the second set too.

Four games later Williams sprinted most of the length of her side of the court to reach a Martic drop shot, feathering a brilliant counter-drop winner which helped alter the mood of the match.

"Everyone is trying to get in better shape, and my goal is to get in better shape each week - and so far so good," commented Williams, who has suffered from Sjogrens syndrome, a condition which affects the auto-immune system.

Williams may though have a tougher task if she is to make further progress, because her next opponent is Petra Kvitova, the third-seeded former Wimbledon champion.

Despite the enduring excellence of Williams' best tennis she has beaten only one top ten player in the last 18 months.

If she needed some sort of an omen, the first day did bring a seeding upset.

Roberta Vinci, the 11th seeded Italian, was beaten 6-3, 6-3 by Tsvetana Pironkova, a Bulgarian whose talent is not at all flattered by a ranking outside the world's top 50.

Pironkova did most things better than an opponent who has not only won nine singles titles but been world number one in doubles.

But 30-year-old Vinci is in woeful form, as she is yet to win a main draw singles match in five attempts this year, while Pironkova, who won her first ever WTA Tour title in Sydney last month, has now won more matches (11) than throughout the whole of last year.

"I learned a lot from all those losses - and Sydney was like a dream for me," said Pironkova. "I feel pretty good."

Other winners included Peng Shuai, the Chinese number two, who came from behind in both sets to beat Nadia Petrova, a former titleholder here, and Peng's doubles partner, Su-Wei Hsieh.

Hsieh, from Taiwan, overcame Flavia Pennetta, a former top ten Italian, 7-5, 6-3, while Peng showed some of the fighting qualities which once made her a top 20 player, recovering from 5-6, 15-30 down in the first set, and from 3-5 in the second to prevail 7-6 (7/5), 7-5.

Later a second seed went out, when Sloane Stephens, the 14th seeded American, was defeated 7-5, 6-1 in chilly late night conditions by Petra Cetkowska, a Czech qualifier ranked outside the top 100.