Wimbledon's empty seats came to the attention of world number one Roger Federer as he cruised into the third round of the Olympic singles tournament with victory over Julien Benneteau.

Blocks of seats reserved for those with accreditation had been conspicuously vacant over the first couple of days, although organisers acted yesterday by making some of them available for fans to buy.

The situation was better today, although Centre Court was not full for any match, including to see crowd favourite Federer, who was untroubled in a 6-2 6-2 victory.

The top seed said: "I had a good time on court. I thought the atmosphere was good. The people here, the way the tickets have been distributed, I think they all feel very fortunate to come to see tennis.

"Obviously there are many areas that are reserved for athletes or VIPs, so it's a bit of a different feel on Centre Court out there to Wimbledon, where you feel every seat is taken at all times. That takes some getting used to."

Federer and Benneteau met in the third round of Wimbledon last month, where the Frenchman almost pulled off a huge shock as he led by two sets to love before the Swiss star turned things around.

Had Benneteau done the same today, he would have won, with the Olympic competition being played over best of three sets until the final, which is best of five.

Federer is the reigning Olympic doubles champion with Stanislas Wawrinka but, were he to win singles gold, he would be following in the footsteps of countryman Marc Rosset, who was the surprise winner in Barcelona in 1992.

Federer, who next meets Uzbekistan's Denis Istomin, added: "I definitely get inspired by the 1992 victory by Marc Rosset. That was huge news in Switzerland.

"But I'm still very far away from all the medals in singles and doubles. Let's not get carried away too quickly. I'm happy with my level of play."

The standout second-round match tomorrow will see second seed Novak Djokovic, who struggled a little bit against Fabio Fognini yesterday, face former world number one Andy Roddick.

The American, who is unseeded here, came through a tight clash with Slovakia's Martin Klizan 7-5 6-4 while another old stager, Australia's Lleyton Hewitt, dug out a 6-3 4-6 6-3 victory over Ukraine's Sergiy Stakhovsky.

Meanwhile, seventh seed Janko Tipsarevic will face 10th seed John Isner in a tasty third-round clash after both won their matches today.

American Isner saw off Tunisia's Malek Jaziri 7-6 (7/1) 6-2 but Tipsarevic had to come from a set down to beat Philipp Petzschner of Germany 3-6 6-3 6-4.

Another attractive clash in two days' time will see eighth seed Juan Martin Del Potro of Argentina face 12th-seeded Frenchman Gilles Simon after their respective victories over Andreas Seppi and Grigor Dimitrov today.

Eleventh-seeded Spaniard Nicolas Almagro is also in the third round, where he will face Tomas Berdych's conqueror Steve Darcis of Belgium, while in the first round there were wins for Richard Gasquet, Juan Monaco, Marin Cilic and Milos Raonic.

With so many stars in action, the match between Blaz Kavcic of Slovenia and India's Vishnu Vardhan attracted little attention, but for the latter it was a huge moment even though he lost 6-3 6-2.

Vardhan is ranked 302nd in the world and got into the draw only because Germany's Philipp Kohlschreiber was a late withdrawal and could only be replaced by someone already in the tournament.

Vardhan is playing doubles with Leander Paes, and he had his partner to thank for taking up the opportunity.

He said: "First of all I am here because of him. Secondly, the day before yesterday he called me up late and said, 'There is a spot in the singles draw and you need to go and sign up first thing in the morning'. I was not aware of that.

"It's a great experience for me. I have never played at Wimbledon. I worked really hard in the match but I could not win. Not many Indians have played singles in the Olympics and I am really happy to be one of them."

And things got even better for Vardhan this evening after he and Paes won their doubles opener 7-6 (7/1) 4-6 6-2 against Dutch pair Robin Haase and Jean-Julien Roger.

Federer and Wawrinka opened their doubles defence with victory over Japan's Kei Nishikori and Go Soeda, but the sixth seeds had to come from a set down to win 6-7 (5/7) 6-4 6-4.

There was disappointment for Novak Djokovic, though, as he and Serbian partner Viktor Troicki were beaten 7-6 (10/8) 6-3 by Swedes Johan Brunstrom and Robert Lindstedt.

Djokovic and Roddick will do battle on Centre Court in singles action tomorrow while elsewhere fourth seed David Ferrer takes on Kavcic and Raonic meets fifth seed Jo-Wilfried Tsonga in a battle of the big hitters.

It was a perfect day for the Williams family as both Venus and Serena won their singles matches and they kicked off the defence of their Olympic women's doubles title with a straightforward victory.

As Wimbledon champion, Serena is one of the favourites for singles gold, and the fourth seed moved through to the last 16 with a 6-2 6-3 win over Urszula Radwanska.

Radwanska is the sister of world number two Agnieszka, who was beaten by Serena in the final of Wimbledon three weeks ago, but the Pole could not take revenge.

By contrast, Venus has struggled for form and good health over the past year as she battles Sjogren's Syndrome and had pushed herself through matches just to qualify for the Olympics.

The Games are very important to Venus, who already has three gold medals to her name, two in doubles with Serena and one in singles from Sydney in 2000.

She rolled back the years today with a superb 6-3 6-1 victory over ninth seed and French Open finalist Sara Errani from Italy, and has her sights firmly set on more medals.

The American said: "It was really great. Grass is my surface and I felt great out there. It's never easy to draw a top seed. I'm unseeded here and now I feel like I'm the number nine seed, and hopefully I'll beat another seed and become their number.

"I fought so much to be here. I know there's a lot of people happy to be here, but I'm not only happy to be here, I want to do something about it too and play well for my country.

"Another gold medal would be amazing. I can't even imagine the feeling, I think my head would be too big and no one would even like me anymore. I've got to get there first. I have two chances and I'll go for it."

Serena is looking for her first singles gold medal and, were she to achieve it, she would be only the second woman after Steffi Graf to have won all four grand slam titles and an Olympic gold in her career.

The 30-year-old has been making sure she follows the rest of the action at the Olympics, and she said: "When I'm not playing I have the TV on watching the swimming, gymnastics. It's so intense and I love every moment."

In the last 16, the American will meet 13th seed Vera Zvonareva, the bronze medallist from Beijing, after the Russian saw off Italy's Francesca Schiavone 6-3 6-3.

Meanwhile, the sisters teamed up this evening for their first-round doubles match against Romanians Sorana Cirstea and Simona Halep, which they won 6-3 6-2.

World number one Victoria Azarenka opened her singles campaign today against Romania's Irina-Camelia Begu, and it was not as straightforward as would have been expected for the Belarusian, who eventually came through 6-1 3-6 6-1.

Two former world number ones will meet in the third round with Serbia's Ana Ivanovic facing Kim Clijsters of Belgium.

Ivanovic, seeded 11th, beat Elena Baltacha of Great Britain 6-4 7-6 (7/5) while Clijsters saw off Spain's Carla Suarez Navarro 6-3 6-3.

Last year's Wimbledon champion Petra Kvitova, the sixth seed here, dropped a set for the second consecutive round but came through 7-5 2-6 6-1 against Peng Shuai, and she next meets Italy's Flavia Pennetta.

Eighth seed Caroline Wozniacki was also pushed before seeing off Belgian Yanina Wickmayer 6-4 3-6 6-3 to set up a meeting with Daniela Hantuchova while there were first-round wins for Wimbledon semi-finalist Angelique Kerber, Sabine Lisicki and Maria Kirilenko.