Top seed Krishnan Sasikiran of Tamil Nadu maintained his lead after beating Prathamesh Mokal of Maharashtra in the 15th round of the 40th National 'A' men's chess championship in Mumbai on Monday.

Sasikiran, who is ranked 40th in the world, chose to play the Ritcher Rauzer variation with black pieces in the Sicilian defence. In the middle game, Sasikiran sacrificed two of his pawns and exposed his rival's King, and with precise game play pocketed full points.

The star from Tamil Nadu seems to be unstoppable with ten wins and four draws to his credit.

However, the upset of the day was caused by M R Venkatesh of Tamil Nadu, who thrashed his statemate and sixth seed R B Ramesh to take his points tally to 8.5.

Venkatesh, who earned his International Master norm a few days ago, played with black pieces and adopted the Nimzo Indian defence. Ramesh, who is also the British champion, erred on his 18th move when played his pawn to g4. This allowed Venkatesh to force his rival's King to the centre and then combined his Rook and two Knights and delivered a mate on the 39th move.

Sasikiran, who has 12 points to his credit, is followed by GMs Pendyala Harikrishna of Andhra Pradesh (10.5 points), Abhijit Kunte of Maharashtra (10 pts), Dibyendu Barua of Bengal (9.5) and IM Venkatesh (8.5).

There were no matches in the women's nationals as it was the rest day for them today.

Results (men's 15th round): A Kunte (10) drew with Arvind Shastry (5), R B Ramesh (6.5) lost to M R Venkatesh (8.5), Saptarshi Roy (7) drew with P Harikrishna (10.5), N Das (8) drew with Tejas Bakre (7.5), P Mokal (4) lost to K Sasikiran (12), S S Ganguly (8.5) drew with P M Thipsay (7), S Kidambi (7.5) bt Lanka Ravi (7.5), D Barua (9.5) bt S Soman (4.5), G B Prakash (6.5) drew with S Satyapragyan (6.5), S Saha (5.5) drew with S Jha (5).