Olympics tennis: Serena and Venus Williams win in singles
American sisters Serena and Venus Williams won their Olympic singles matches in straight sets at Wimbledon.
Serena beat Poland's Urszula Radwanska 6-2 6-3 to reach the last 16, while Venus beat Italy's French open finalist Sara Errani 6-3 6-1.
World number one Victoria Azarenka survived a mid-match blip to beat Irina-Camelia Begu of Romania winning 6-1 3-6 6-1 in the first round.
In the men's singles, Roger Federer comfortably beat Julien Benneteau.
The world number one from Switzerland needed only 58 minutes to beat his French opponent 6-2 6-2.
Federer also secured a victory in the men's doubles alongside playing partner Stanislas Wawrinka, beating Kei Nishikori and Go Soeda of Japan, 6-7 (5) 6-4 6-4.
Venus Williams, who won gold at the Sydney Olympics in 2000, will now play Canada's Aleksandra Wozniak in the second round.
"I'm unseeded here and now I feel like I'm the number nine seed. Hopefully I'll beat another seed and become their number," she said.
"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."
Andy Roddick booked a second-round meeting with second seed Novak Djokovic after beating Slovakia's Martin Klizan 7-5 6-4.
"We're both comfortable with this venue so it will produce a good match," said former world number one Roddick of his match with Djokovic.
"For me, it's just an honour to be asked to play at the Olympics. I was happy when London got chosen. It's a place that I know well and I know how to play here. All things combined, it is a great opportunity for me."