21:15 CET - Novak Djokovic has announced he will not compete at next week's Paris Masters.
Read more about that breaking news here.
20:58 CET - Moving back over to Basel, second seed Ben Shelton has moved into the second round after battling past qualifier Kamil Majchrzak 6-7, 6-3, 7-6.
The American saved two match points on his way to victory in Switzerland.
20:07 CET - Ninth seed Denis Shapovalov has marched on with a 6-7, 6-0, 7-6 win over Marcos Giron in Basel, while Lorenzo Musetti has beaten Hamad Medjedovic 6-4, 6-3 in Vienna.
19:21 CET - Argentina's Francisco Cerundolo is the latest man through in Vienna, thanks to an emphatic 6-3, 6-1 win against Alex Michelsen.
18:38 CET - Cameron Norrie has advanced to the next round in Vienna after a shock 6-2, 6-7(5), 6-2 victory over seventh seed Andrey Rublev.
Tomas Martin Etcheverry is also through in Austria, with the Argentine seeing off Nicolai Budkov Kjaer 6-3, 6-3.
18:04 CET - What was perhaps the standout clash of the day, between Stefano Tsitsipas and Lorenzo Musetti in Vienna, has been called off, with the Greek player pulling out with an injury and the Italian instead facing lucky loser Hamad Medjedovic.
17:56 CET - Joao Fonseca has advanced in Basel with a hard-fought 7-6, 6-3 win over reigning champion Giovanni Mpetshi-Perricard, setting up a clash with fellow young star Jakub Mensik.
17:15 CET - In the last matches of the day in Guangzhou, fourth seed Alexandra Eala has been beaten 2-6, 6-4, 6-4 by qualifier Claire Liu and fifth seed Alycia Parks has lost 7-5, 7-5 to Ajla Tomljanovic.
16:26 CET - Home favourite Filip Misolic is through in Vienna, with the wildcard battling through two tight sets to defeat Camilo Ugo Carabelli 7-5, 7-6(6).
Meanwhile, in Basel, Marin Cilic has seen off the challenge of experienced Belgian David Goffin, 7-6(9), 7-5.
13:52 CET - Reilly Opelka is the first winner of the day in Basel after a relatively routine 6-3, 6-4 triumph over Sebastian Baez.
Meanwhile, in Guangzhou, American pair Katie Volynets and Caty McNally have progressed after three-set wins over Katarzyna Kawa and Kaja Juvan, respectively.
11:33 CET - The final match of the day in Tokyo has been won by Sofia Kenin, last year's runner-up, with the world number 25 beating wildcard Moyuka Uchijima 6-1, 6-3 on the latter's home turf.
09:47 CET - Japanese wildcard Wakana Sonobe is through on home soil after a 6-4, 6-3 win against Nikola Bartunkova in Tokyo, while sixth seed Yulia Putintseva and Lulu Sun have both advanced in Guangzhou.
08:04 CET - There's been plenty of early action in Tokyo, with Leylah Fernandez battling past Maria Sakkari 7-6(5), 6-4 and ninth seed Victoria Mboko seeing off Bianca Andreescu 6-3, 6-3 in an all-Canadian affair.
Diana Shnaider is also through after an emphatic 6-3, 6-1 triumph over Dayana Yastremska in just 64 minutes.
Meanwhile, in Guangzhou, Ann Li, Camila Osorio and Ella Seidel have all moved into the next round after straight-set victories.
Looking ahead to the rest of the day, the standout clash comes in Vienna, where fourth seed Lorenzo Musetti comes up against Stefanos Tsitsipas.
That clash is due to get underway around 17:30 CET, while Alexander Zverev, Ben Shelton and Andrey Rublev are among the other big names in action throughout the day.
07:45 CET - Good morning and welcome to our coverage of today's tennis!