GWANGJU, South Korea, July 16 (Xinhua) -- Defending champion United States and power-houses Hungary, Russia, Spain and Italy keep their unbeaten run after the second preliminary matches of women's water polo at the 18th FINA World Swimming Championships here on Monday.

United States trounced the Netherlands 12-9, New Zealand upset South African 14-2 in Group A while Hungary had a narrow victory over Canada 15-14 and Russia swept the host team South Korea 30-1 in Group B.

Spain cracked down Kazakhstan 18-6 and Greece romped Cuba 20-4 in Group C.

In Group D, Italy stayed on top as they beat Japan 9-7 and China lost to Australia 12-14 after close battle 4-4, 3-5, 3-3, 2-2.

"We had a close and good game. We made some mistakes in the defence that cost our victory. We should strengthen on that in our next game against Italy," said Wang Xinyan, captain of China.

The third round of group matches of women's water polo will be held on July 18.