A day after scoring a memorable victory, top seed Grandmaster Koneru Humpy suffered a shock defeat at the hands of Tatiana Kosintseva of Russia in the second game of the third round in the Women's World Chess Championship in Elsita, Kalmykia, in Russia on Thursday.

With their scores now tied, both Humpy and Kosintseva will fight it out in two tie-break games of 25 minutes each for a place in the next round.

Kosintseva will have the advantage of playing white in the first game of the tie-break.

Like Humpy, Ketino Kachiani of Germany also failed to defend her full point lead against 14-year-old Kateryna Lahno of Ukraine even though former world women's champion Maya Chiburdanidze of Georgia and compatriot world junior girls' champion Nana Dzagnidze sailed through to the quarterfinals.

Dzagnidze scored her second successive victory over Maia Lomineishvili, also of Georgia, while Chburdanidze held Jana Jackova of Czech Republic. Also qualifying to the last 16 was World Cup winner Xu Yuhua of China who showed the exit door to Elisabeth Paehtz of Germany.

Humpy started with a bad opening, which was handled quite well by her talented opponent, and struggled in the middle game with under-developed pieces. Humpy eventually lost a long drawn endgame after she was forced to part with a pawn.

Maia Chiburdanidze has not been playing much these days but still has not lost the magical touch that saw her ruling world chess for over a decade.

Trailing after losing her first game, Jana Jackova of the Czech Republic proved no match for her illustrous rival even though she tried all the tricks in her bag.

It was a King's Indian structure by transposition where Maia's experience came in handy as she contained Jackova's pieces to make a decisive headway.

In what was a desperate measure, Jackova sacrificed a piece to open up the position but Chiburdanidze returned the favour a few moves later to emerge a pawn plus.

Subsequent exchanges forced Jackova on the defensive and in a clearly inferior position she had no choice but to accept  the draw proposal by Chiburdanidze.

Nana Dzagnidze was in her element against Serbian Natasa Bojkovic, who came quite close to draw the game.

It was an irregular queen pawn game and Bojkovic was completly at sea in working out the right plan in the middle game. As a result, Dzagnidze's rooks moved to the seventh rank pretty early in the game and did most of the damage.

With the draw threat looming large vide perpetual checks, Bojkovic made the decisive error that caught her king on the  wrong foot.

Xu Yuhua showed tremendous temperament and skills to oust Elisabeth Paehtz of Germany who played the black side of a Sicilian defence.

The Chinese got a reasonable position after the opening and pressed for an advantage in the middle game.