American sisters Venus and Serena Williams stormed into the semi-final s of the women's doubles at Wimbledon, beating the Indo-American pair of Sania Mirza and Bethanie Mattek 6-4, 6-3 in the quarter-finals on Wednesday.

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The 11th seeded Williams, both of whom are already in the singles semi-finals, proved too strong for 13th seeds Sania and Mattek.

They were up 5-3 in the first set before rain intervened at deuce in the ninth game.

After the break the Indo-American pair served out the game but the Williamses held serve in the next to take the set.

In the second set, Sania and Mattek looked liked making a match of it as they broke in the second game to go 2-0 up. But Venus and Serena effected breaks in the fifth, seventh and ninth games to cruise home at 6-3.