Serena Williams continued her campaign for an eighth Wimbledon title after the 37-year-old American bested Germany's Julia Goerges. Photo: Ben Curtis/AP Photo

LONDON  World number one Ashleigh Barty maintained her impressive form with a comprehensive 6-1, 6-1 triumph over Britain's Harriet Dart to enter the last 16 stage at Wimbledon on Saturday. 

The 23-year-old Australian extends her unbeaten run to 15 matches and is the first female from her country to reach the second week of the tournament since 2010. 

"I felt like I served really well today," said Barty.

"I did my best to get a quick start. 

"It's a first for me (entering the second week) and new territory but really excited to be here in singles for the first time." 

Meanwhile, Serena Williams continued her campaign for an eighth Wimbledon title after the 37-year-old American bested Germany's Julia Goerges 6-3, 6-4 to enter the fourth round at Wimbledon. 

Barty stormed into a 5-0 lead and served out the set with three aces in just 25 minutes. 

The 22-year-old Dart, who is ranked 181 places below top seed Barty, wilted with a netted backhand to concede a 2-0 deficit in the second set. 

Barty saved four break points at 4-1 and rallied to victory inside an hour.  

American Alison Riske is Barty's next opponent after she bested Swiss Belinda Bencic 4-6, 6-4, 6-4.  

Williams rallied to the first break at 4-2 before wrapping up the first set with a cross-court forehand after half an hour. 

Goerges, who was beaten in the semi-finals last year by Williams, fired a long return to fall a break behind in the second set and was resigned to defeat after 72 minutes. 

The 23-time grand slam winner will play Carla Suarez Navarro on Monday following the Spaniard's 6-3, 6-3 success over American Lauren Davis. 

Petra Kvitova also progressed to the last 16 after the Czech, who is a two-time Wimbledon champion cruised to a 6-3, 6-2 win over Poland's Magda Linette. 

Kvitova will meet either American ninth seed Sloane Stephens or Britain's home favourite Jo Konta next. 

Belgium's Elise Mertens is through to the second week as she dismissed China's Qiang Wang 6-2, 6-7 (9-11), 6-4. 

In the men's draw, Japanese eighth seed Kei Nishikori advanced after he surpassed American Steve Johnson with a 6-4, 6-3, 6-2 victory for his 400th match win at Tour-level. 

American Sam Querrey defeated Australia's John Millman 7-6 (7-3), 7-6 (10-8), 6-3 to enter the second week of the tournament for the fourth time in his 12th appearance at the tournament. 

Eight-time champion Roger Federer and world number two Rafael Nadal continue their Wimbledon campaigns on Centre Court later on Saturday. 

dpa