22:08 CET - Our final game of the day has come to an end with third seed Tomas Machac forced to retire late in the third set against Cameron Norrie, with the score at 3-6, 6-2, 4-3. Perhaps the Czech star has one eye on next week's French Open?
20:32 CET - Looking for some form on the clay this week, Felix Auger-Aliassime has defeated big-serving Frenchman Giovanni Mpetshi Perricard, winning 6-2, 6-4 in just under an hour and a quarter.
20:01 CET - In her fourth time of trying, Anna Kalinskaya has finally beaten Jessica Pegula, putting in a really assured and confident performance to down the American, 4-6, 6-4, 6-2 in Strasbourg.
19:44 CET - Novak Djokovic looked in really good touch in his opening round match in Geneva, dispatching Marton Fucsovics, 6-2, 6-3, in an hour and a quarter, as he continues his quest for a 100th ATP title.
Alexei Popyrin also progressed with a 6-4, 6-3 win over Jacob Fearnley in Switzerland.
19:02 CET - Top seed and home favourite Alexander Zverev is out of Hamburg after the world number three came up short against Alexandre Muller, losing 3-6, 6-4, 6-7(5).
18:35 CET - Hubert Hurkacz and Matteo Arnaldi have progressed in Geneva after straight-set victories over Arthur Rinderknech and Fabian Marozsan respectively.
17:54 CET - Danielle Collins has sealed a quarter-final berth in Strasbourg after coming from behind to defeat Emma Raducanu 4-6, 6-1, 6-3 in two hours and 19 minutes.
The American will face either compatriot Jessica Pegula or Anna Kalinskaya in the last eight.
16:40 CET - Flavio Cobolli is safely through in Hamburg, with the Italian seeing off fifth seed Alejandro Davidovich Fokina in two closely fought sets, 6-4, 7-5.
Elsewhere, Sebastian Ofner has progressed in Geneva after a 7-6(2), 7-6(4) triumph over Portugal's Nuno Borges.
15:45 CET - No. 3 seed Andrey Rublev is the next player to win in Hamburg, overcoming 17-year-old wildcard Justin Engel, 6-3, 7-5.
Tomas Martin Etcheverry also downed fellow Argentine Camilo Ugo Carabelli, 6-4, 6-4, to move into the quarters in Germany.
14:55 CET - No. 2 seed Emma Navarro has eased into the Strasbourg quarter-finals, coasting past Anna Blinkova, 6-4, 6-1, to set up a meeting with Beatriz Haddad Maia.
Meanwhile, over in Rabat, Jessica Bouzas Maneiro and Ann Li both won to move into the last eight.
14:08 CET - Jiri Lehecka has claimed a fine win in Hamburg, beating clay-court expert Francisco Cerundolo, 7-5, 6-2, to move into the quarter-finals.
Karen Khachanov has also progressed in Geneva after his opponent, Kei Nishikori, withdrew from their contest before the pair were due to resume their match today.
13:50 CET - Roberto Bautista-Agut has knocked out second seed Frances Tiafoe in Hamburg, with the experienced Spaniard prevailing 6-2, 6-3 in just 87 minutes.
13:15 CET - World number four Taylor Fritz is safely through in Geneva, with the American battling past Quentin Halys in two competitive sets, 6-4, 7-6(5).
Meanwhile, in Strasbourg, ninth seed Beatriz Haddad Maia has progressed after a hard-fought 7-6(3), 6-3 victory over Ashlyn Krueger.
09:34 CET - We're just under two hours away from play getting started in Geneva, where top seed Taylor Fritz takes on Quentin Halys at 11:30 CET.
Later on, Novak Djokovic begins his campaign in Switzerland against Marton Fucsovics, while Alexander Zverev, Andrey Rublev and Frances Tiafoe headline the action at the ATP event in Hamburg.
On the WTA Tour, Jessica Pegula and Emma Navarro take to the court in Strasbourg, while there's also plenty of action at the WTA 250 in Rabat.
Check out the full schedule for tournaments in Geneva, Hamburg, Strasbourg and Rabat via the links.
08:50 CET - Good morning and welcome to our coverage of today's tennis!