The 62-year-old disco icon is reportedly in a coma after contracting pneumonia, according to his website.
"Sadly the reports are true that Robin has contracted pneumonia and is in a coma," says a message on the RobinGibb.com homepage. "We are all hoping and praying that he will pull through."
While specific details regarding Gibb's condition are being kept under wraps (rumors that doctors found a secondary tumor are unconfirmed), sources told the U.K. Sun that the "Stayin' Alive" songster is very ill and his family is keeping vigil at his bedside in a London hospital.
News of Gibb's latest health scare comes just a few weeks after he underwent emergency surgery March 26 to remove a "blood clot that caused perforation." It was a procedure that followed an earlier operation for a twisted intestine, and was said to be unrelated to his recent battles with cancer.
Prior to the surgery, Gibb had hoped to be well enough to attend the London premiere of his first classical work, Titanic Requiem, Tuesday, but his condition prevented him from attending.
Gibb's son, Robin-John Gibb, read a message to the audience at the event and revealed that his father was still in the hospital.
"He sends all his love," Robin-John said before the performance began. "We are all praying for him and hoping he has a speedy recovery."
Despite his many health scares, Gibb had remained in high spirits regarding his health, telling BBC Radio 2 in February he had made a "spectacular" recovery from a serious illness (he didn't specify the malady).
"Well, it's all simple," Gibb said. "I was diagnosed with a growth in my colon. It was removed. And I've been treated for that by a brilliant doctor, and in their words 'the results have been spectacular.'"
"[The growth in my colon] is almost gone and I feel fantastic," Gibb continued. "Really from now on, it's just what they could describe as a 'mopping-up' operation. I am very active and my sense of well-being is good."
According to the Daily Mail, however, Gibb continued to have issues with a twisted bowel, which was thought to have led to his hospitalization last month.
Gibb's rep had no comment on his current condition.
—Reporting by Marcus Mulick
(Originally published, April 14, 2012, at 10:36 a.m. PT)