The 33-year-old, who topped US and UK charts last week with comeback single “Easy On Me,” took to Twitter with the message “Oiii Oiiiiiiiiiiiii,” sharing the July 1 and 2 concert dates and the pre-sale link on her website.
The shows, part of the BST Hyde Park concerts, are Adele’s first since 2017.
However, several British media outlets reported the site had crashed, quoting fans as saying they were unable to register for the pre-sale.
“I tried to subscribe for more than 2 hours but still couldn’t do it,” one wrote on Twitter.
“Trying to sign up for pre-sale for @Adele at Hyde Park but even signing up ain’t working haha! I think winning the lottery is easier than getting tickets for these concerts,” another wrote.
When clicked, the pre-sale registration tab on the website brought up the message “Currently unavailable, please try again later.” Some fans said they had succeeded in registering.
Other performers at the Hyde Park concerts include Elton John, Duran Duran and Pearl Jam.
Adele is due to release her fourth studio album “30,” her hotly anticipated follow-up to 2015’s Grammy Award winning “25,” in November.