Carvalho was examined by medical staff following his technical knockout loss to Charlie Ward, a team mate of UFC featherweight champion Conor McGregor.

The 28-year-old's condition deteriorated and he was brought to a Dublin's Beaumont hospital, where he had a brain operation.

"It is with great sorrow and sadness that we write these words, that the death of the athlete Joao Carvalho has occurred after 48 hours in critical condition," team boss Vitor Nobrega announced in a post on its Facebook page.

John Kavanagh, who coaches McGregor and Ward, expressed his condolences in a Facebook post and said the Irish Amateur Pankration Association (IAPA), which governs the sport of MMA in Ireland, was working to establish exactly what led to Carvalho's death.