The first round of tickets for Harry Potter and the Cursed Child have sold out, with producers releasing a second batch, available to fans who registered for priority booking.
The first four months of tickets, for performances from 7 June-18 September 2016, went on sale at 11:00 GMT, selling out in several hours.
Many fans experienced technical difficulties trying to buy tickets.
The play is based on an original JK Rowling story.
It has been co-written by Jack Thorne and director John Tiffany,
Billed as the "eighth Harry Potter story and the first official Harry Potter story to be presented on stage", the two-part play makes its world premiere at the Palace Theatre in London's West End next summer.
Producers say more than 120,000 fans went online this morning to try and buy tickets, some of which appeared on re-sale ticket websites soon after, priced at more than £1,000.
The play's official Twitter account warned fans not to use the sites, writing: "Please do not attempt to resell your tickets on alternative platforms, as patrons will not be admitted into the theatre."
Tickets for the second round of dates, until January 2017, are now on sale to people who registered for priority booking. Producers say a third booking period will be opened up on Friday when seats go on sale to the general public.
Many fans expressed their frustration on Twitter, complaining of hours spent online trying to buy tickets.
Em Maree wrote: "Finally got my three tickets for the #CursedChild play but am shocked by the shambles that was the booking. 4 hours is a joke!"
Nikki Alden was one of many people reporting being bumped out of the queue, writing: "There was and error on the site right before I was about to pay for my tickets and now I'm 33,084TH in line!!!"
Meanwhile Lisa Cooke directed her frustrations directly at Potter author Rowling, writing: "This play better blow my mind @jk_rowling @HPPlayLDN ... Never been so stressed buying tickets before #CursedChild."
Producers told the BBC "the vast majority of customers had their bookings processed within an hour."
They added: "Customers who are having difficulties with the online booking system can be assured we are doing everything we can to ensure the process is a smooth and efficient as possible."
Once tickets sell out, there will be a weekly and daily lottery for all performances nearer the time. Both parts are designed to be watched in the same day - matinee and evening - or on two consecutive nights.
Previews begin on 7 June 2016 with the official opening performances of both parts on 30 July.
The story takes place several years on from the end of the last Potter book, when Harry is an overworked employee of the Ministry of Magic, a husband and father of three children.
His youngest son Albus has to take on the weight of the family legacy, and "both father and son learn the uncomfortable truth: sometimes, darkness comes from unexpected places."