Former world No. 1 Caroline Wozniacki was among Tuesday's round-robin winners at the $750,000 Tournament of Champions.

The top-seeded Wozniacki, of Denmark, waltzed past fifth-seeded Su-Wei Hsieh of Taipei 6-2, 6-2 on the indoor hardcourts at Armeets Arena. Wozniacki and Hsieh are both two-time champions on the WTA this year.

Also on Day 1, fourth-seeded Italian Roberta Vinci whipped seventh-seeded Slovak Daniela Hantuchova 6-1, 6-2 and eighth-seeded Bulgarian crowd favorite Tsvetana Pironkova overcame sixth-seeded Chinese Zheng Jie 2-6, 6-4, 7-6 (9-7).

On Wednesday, Wozniacki will battle Vinci, while second-seeded Russian Nadia Petrova will take on Zheng and third-seeded Russian Maria Kirilenko will be opposed by Pironkova.

The Tournament of Champions is the finale for the WTA's International Series, with the six highest-ranked players who have won an International title this year -- and two wild cards -- comprising the eight-woman field. The four- player Serdika Group features Wozniacki (1-0), Vinci (1-0), Hsieh (0-1) and Hantuchova (0-1), while the four-player Sredets Group features Petrova (0-0), Kirilenko (0-0), Zheng (0-1) and Pironkova (1-0).

The tournament format will see two round-robin groups play out over the first four days, with the semifinals on Saturday and the final on Sunday.

Serbian star Ana Ivanovic topped Spaniard Anabel Medina Garrigues for her second straight title at this event in last year's finale in Bali, which also hosted the tournament in 2009 and 2010.

The current host Sofia will also stage this event next year and in 2014.