Image copyright Reuters Image caption Rob Ford is running for re-election in October

Toronto Mayor Rob Ford has been admitted to hospital with a tentative diagnosis of a tumour after suffering months of abdominal pain.

Mr Ford told doctors at Humber River Hospital the pain had persisted for at least three months and had worsened in the past 24 hours, the hospital said.

The embattled mayor is standing for re-election on 27 October despite repeated calls for him to step down.

Last year, he admitted to using crack cocaine in a "drunken stupor".

Mr Ford returned to work earlier this year after about two months of treatment for drug and alcohol abuse, which he described as life-saving.

In a statement, Humber River Hospital said "examination and investigation has resulted in a working diagnosis of a tumour" for Mr Ford.

"The mayor has been admitted to allow for further investigation to obtain a definitive diagnosis."

In a press conference on Wednesday, Dr Rueben Devlin said Mr Ford came in when the pain "became unbearable for him".

Dr Devlin said doctors would need to determine the type of tumour by doing a biopsy. He did not say how long Mr Ford would be in hospital.

Councillor Doug Ford, the mayor's brother and campaign manager, said his brother was in good spirits and they would not be making any comments about the status of his election campaign at the moment.

"I just wanted to thank the well-wishers for all of the calls," Doug Ford said, asking the reporters assembled at the press conference to "leave us alone for a couple of days".

Mr Ford was hospitalised in 2009 for a tumour on his appendix, the Toronto Sun reported.