Li Na returns a shot against Zheng Jie during their match at the Indian Wells WTA tennis tournament in Indian Wells, California, March 10, 2012. [Photo/CFP]

INDIAN WELLS, California - Top seed Victoria Azarenka charged into the fourth round of the Indian Wells WTA tournament by crushing Svetlana Kuznetsova 6-1 6-2 on Sunday, improving her unbeaten record to 19-0 this year.

The Belarusian world number one, who had battled through her opening match against Germany's Mona Barthel 6-4 6-7 7-6, broke Russian Kuznetsova three times in the first set and twice in the second.

Serving for the match at 5-2, Azarenka went 40-15 up before double-faulting but then sealed the win on the next point when her opponent's backhand flew long.

"I am really happy with the way I played today," a smiling Azarenka said in a courtside interview after dispatching Kuznetsova in just one hour.

"I really turned it around from the survival the last time around," she added, referring to her three-hour battle with Barthel on the stadium court in the second round.

Victoria Azarenka of Belarus returns a shot to Svetlana Kuznetsova of Russia during their women's singles match at the the Indian Wells WTA tennis tournament in Indian Wells, California, March 11, 2012. [Photo/Agencies]

Azarenka, who clinched her first grand slam crown at the Australian Open in January, will next meet Germany's Julia Goerges, a 6-3 6-4 winner against Spaniard Anabel Medina Garrigues.

French Open champion Li Na beat fellow Chinese Zheng Jie 6-1 6-3, her first victory over her compatriot in five career meetings.

"It's always tough to play a same-country player because we know each other a lot," said Li, who became the first Asian woman to win a grand slam singles title with her victory over Italian Francesca Schiavone in Paris last year.

"We stay in the national teams so we practise every day and travel all of the time, so it's very tough. But I was so happy because it's the first time I beat her.

"The last meeting was six years ago, so six years can change many things," added Li, who is affectionately known as "Big Sister Na" and "Golden Flower" in China.