Muhammad Ali has been readmitted to hospital for follow-up care for a urinary tract infection, his second spell in the last four weeks.

Family spokesman Bob Gunnell said the three-time former heavyweight boxing champion was in a stable condition after being admitted to an undisclosed hospital earlier this week and is expected to be released on Friday.

Ali, who is 73 on Saturday, was admitted to hospital on 20 December with what was initially believed to be a mild case of pneumonia, but later turned out to be a severe urinary tract infection.

"There were further issues with the earlier diagnosis of a urinary tract infection," Gunnell told Press Association Sport.

Ali, considered by many to be the greatest boxer of all time, retired from the sport in 1981 and has suffered with Parkinson's since the mid-1980s.