Elton John is postponing his summer tour, including an outdoor concert in London's Hyde Park on Friday, after being diagnosed with appendicitis requiring surgery.

During recent concert dates across Europe, the 66-year-old British singer-songwriter felt ill and consulted doctors for medical testing.

He learned he was suffering from an inflamed appendix and surrounding abscess, with doctors advising him to postpone forthcoming shows on his European tour, according to a statement issued Tuesday.

John "is currently undergoing a course of intensive antibiotics and is expected to undergo surgery in the U.K. in the coming weeks, once doctors can be confident they have sufficiently reduced toxins within the inflamed appendicitis site," read a statement on his website.

Along with Friday's show in London, in which he was set to join Elvis Costello and Ray Davies, John's postponed dates include gigs in Italy, Germany, Spain, France and Monaco.

"Elton is incredibly disappointed to postpone these tour dates," a spokesman said in the statement.

Pending John's full recovery, "he is eager to be back on top form and return to play the remaining shows starting in early September 2013."

The singer's new album, The Diving Board, is set for release in September.

Last month, he and writing partner Bernie Taupin were honoured at the U.S. Songwriters Hall of Fame gala. Earlier this year, John and his Canadian-born husband David Furnish announced the birth of Elijah, their second son (born to a surrogate mother). The couple also have a toddler, Zachary.