Venus, Serena Williams off to winning start

Defending champions Venus and Serena Williams have flown into the second round of the women's Olympic doubles thanks to a straight-sets triumph over the Romanian team of Sorana Cirstea and Simona Halep.

The two-time gold medallists broke twice in the opening set to claim it 6-3.

With a large crowd descending on Court 2, the dominant Americans took the second 6-2 to seal the win in just one hour and five minutes.

The sisters are expected to face a stiffer challenge in the second round when they play the German team of Sabine Lisicki and Angelique Kerber.