Viswanathan Anand maintained top form and demolished Alexander Morozevich of Russia to emerge sole leader after the end of the fourth round in the Morelia-Linares chess tournament in Morelia, Mexico.

The Indian ace, who had beaten Norway's Magnus Carlsen in the third round, came out trumphs in a well-contested battle against the Russian and took his tally to three points out of a possible four in this category-20 double round-robin event between eight players.

The Indian ace is now followed by Carlsen, who came up with his second victory in the event at the expense of overnight joint-leader Vassily Ivanchuk of Ukraine to move to 2.5 points, while Levon Aronian of Armenia, Peter Leko of Hungary and Russian Peter Svidler inched to two points after draws in the third round game.

Top seed Veselin Topalov of Bulgaria is next in line on 1.5 points along with Ivanchuk, while Morozevich is at the bottom of the table on just one point from three games.

Ten more rounds remain in this second major of the year.

Anand baffled Morozevich from a level position arising out of Ruy Lopez opening, where the Indian played white.

To his credit, Morozevich held out Anand's aggressive intentions for a long time in the middle game. However, the Russian failed to be consistent enough around the end of first time control and Anand soon seized the initiative and knocked down two black pawns in quick time.

Morozevich was no match thereafter and resigned on move 59.

Contrary to the first three rounds that produced just one decisive game each, the fourth round had two decisive games and yet again the youngest participant in the fray, Carlsen, was the cynosure of all eyes.

Ivanchuk's form suffered a real low in this contest, moving his one knight five times in the opening itself and using around one hour for the first 12 moves.

Magnus got a slightly better position playing black and even as the game was stretched for a long time the Norwegian retained his advantage. The game lasted 60 moves.

Aronian apparently had some chances against Leko when the latter sacrificed an exchange in the early middle game arising out of a Queen's gambit declined where the former played white.

Leko had to find correct exchanges in the final stages to force a draw and he achieved it.

Playing white against Svidler, Topalov got slightly better prospects out of the opening but missed the thread later to allow Svidler to equalize easily.

When the draw was agreed to, the pundits of the game even thought that Svilder had some chances.

Results, round 4: Viswanathan Anand (Ind, 3) beat Alexander Morozevich (Rus, 1); Vassily Ivanchuk (Ukr, 1.5) lost to Magnus Carlsen (Nor, 2.5); Veselin Topalov (Bul, 1.5) drew with Peter Svidler (Rus, 2); Peter Leko (Hun, 2) drew with Levon Aronian (Arm, 2).

The moves: V Anand v/s Alexander Morozevich

1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Be7 6. Re1 b5 7. Bb3 d6 8. c3O-O 9. h3 Nb8 10. d4 Nbd7 11. Nbd2 Bb7 12. Bc2 Re8 13. Nf1 Bf8 14. Ng3 c6 15. Nf5 Qc7 16. dxe5 dxe5 17. Nh2 c5 18. Qf3 c4 19. Bg5 Re6 20. Rad1 Nc5 21. Bxf6 Rxf6 22. Ng4 Re6 23. Nge3 Qa5 24. a3 g6 25. Nd5 Rd8 26. Qg3 Rd7 27. Nfe3 Qd8 28. Qf3 Bg7 29. a4 Red6 30. axb5 axb5 31. g4 Qh4 32. Ra1 Ne6 33. Qg3 Qxg3+ 34. fxg3 Nc5 35. h4 h6 36. Ra5 Bc6 37. Nb4 Bxe4 38. Bxe4 Nxe4 39. Rxb5 Nd2 40. Kg2 e4 41. Re2 Bf8 42. Ned5 e3 43. Nxe3 Re6 44. Nbd5 Nb3 45. Nf4 Rc6 46. Nxc4 Rxc4 47. Rxb3 Kg7 48. Rb5 Bc5 49. g5 hxg5 50. hxg5 Be7 51. Kf3 Bd8 52. Re4 Rc6 53. Kg4 Rd2 54. Rd5 Rxd5 55. Nxd5 Re6 56. Rxe6 fxe6 57. Nf4 Kf7 58. Nd3 Bc7 59. Kf3 black resigned.