Poland's Radosław Wojtaszek held world chess champion Magnus Carlsen to a draw in their opening game ©FIDE/Anastasiia Kurulkova

World number one Magnus Carlsen was held to a draw in his first game with Poland's Radosław Wojtaszek as the fourth round of the Chess World Cup in Sochi got underway.

The Norwegian - who is the reigning world champion - was forced into a draw for the first time during the tournament in Russia by 33rd seed Wojtaszek.

Carlsen is just one of four top-10 seeds still left in the draw - joined by Russian fifth seed Alexander Grischuk, France's seventh seed Maxime Vachier-Lagrave and Russian 10th seed Sergey Karjakin.

Grischuk was held to a draw today by Ukraine's 37th seed Anton Korobov, as was Vachier-Lagrave against Indian 90th seed Rameshbabu Praggnanandhaa, who is just 15 years old.

Karjakin drew with 23rd seed and compatriot Vladislav Artemiev.

Iranian 86th seed Amin Tabatabaei has taken the lead in his match against Indian 11th seed Pentala Harikrishna, while Azeri Vasif Durarbayli is a game up in his match against Uzbekistan's Nodirbek Abdusattorov.

Abdusattorov shocked Dutch fourth seed Anish Giri in the previous round.

In the inaugural Women's Chess World Cup, which is also taking place in Sochi, Russian top seed Aleksandra Goryachkina finds herself down 1-0 against Bulgarian 16th seed Antoaneta Stefanova.

Goryachkina's second-seeded compatriot Kateryna Lagno drew her opening fourth-round game with Kazakh 50th seed Bibisara Assaubayeva, and Ukraine's third seed Mariya Muzychuk also drew against Russian 14th seed Alexandra Kosteniuk.

Muzychuk's older sister Anna, who is seeded fourth, also drew her opening game of the round against German 20th seed Elisabeth Pähtz.