Seve Ballesteros remained "under observation" in Madrid's La Paz hospital last night after undergoing a third brain operation.

Doctors declared the surgery a success and stressed there had been no complications in the procedure to alleviate pressure on the brain caused by an edema, and to remove remaining tumour tissues.

Ballesteros, the 51-year-old five-time major winner, was diagnosed with a tumour earlier this month and before yesterday's surgery he had already undergone two operations — the second to reduce swelling on the brain.

Hospital officials confirmed Ballesteros was in theatre for over six hours.

A statement from the hospital last night read: "The patient Mr Severiano Ballesteros has been subjected to a new surgery that ended at 1700 today with no complications occurring.

"The patient is stable... and is currently under observation in the intensive care unit."