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!