The WTA tour has been suspended until May 2 due to the coronavirus pandemic.
Forthcoming tournaments in Stuttgart, Istanbul and Prague will not take place as planned.
The latest cancellations follow those of the Indian Wells Open, Charleston Open and Miami Open in the United States, along with events in Bogota and Guadalajara.
The tour will make a decision on the status of its remaining European clay court tournaments later this week.
A WTA statement said: "Due to the ongoing global coronavirus outbreak, the WTA tournaments in Stuttgart, Istanbul and Prague will not be held as scheduled.
"We regret this is the case for all of our loyal fans, players, sponsors and all those who support women's professional tennis.
"At this point in time, the WTA Tour is now suspended until May 2. We will make a decision in the week ahead regarding the remaining WTA European clay court events and will continue to monitor this situation closely and its impact on the 2020 WTA Tour season."