Top seed Koneru Humpy remained in the hunt for top spot with a hard-fought victory over former world champion Maia Chiburdanidze of Georgia in the sixth round of the IS Bank Ataturk Women's Grand Prix chess tournament in Istanbul.

Registering her fourth win in the tournament apart from two draws, Humpy took her tally to five points out of a possible six and remained in the joint second spot.

Overnight leader Yifan Hao of China defeated Martha Baquero Fierro of Ecuador to remain in sole lead on 5.5 points.

Humpy and Zhao Xue of China, who defeated Betul Cemre Yildiz of Turkey in the sixth round, are a half point adrift of the leader.

Elina Danielian of Armenia accounted for former world champion Antoaneta Stefanova of Bulgaria to hold on to the fourth spot on four points with five rounds still remaining in the tournament.

In the other games of the day, Zeinab Mamedjarova scored her first victory defeating Shen Yang of China while Pia Cramling of Sweden signed peace with Marie Sebago of France [Images].

Humpy opted for a side variation in the Queen pawn opening and secured an advantage with her central pawns becoming dominant. The middle game saw Maia struggling to find a safe haven for her pieces and in her bid for counterplay, the Georgian won a queen side pawn allow white to initiate an attack on the king side.

Almost in a heap, the pieces changed hands and suddenly Maia realised that in the process her knight had been left unattended in the middle of the board. Even though she had two pawns for the knight, the Georgian knew it was a futile exercise to carry on and resigned on the 42nd move.