The 93-year-old former leader who ruled the southern African nation for 37 years, resigned after the army and his ruling ZANU-PF party turned against him when it became clear that his 52-year-old wife, Grace, was being groomed as his successor.
Mugabe left Harare with his wife and aides on Monday evening, a Zimbabwe state security official said this week. He was expected to also visit Malaysia where his daughter is expecting a child.
An Air Zimbabwe flight arrived in Singapore on Tuesday.
Mugabe visited a private hospital in central Singapore on Wednesday with an entourage that included his security guards, the sources who were familiar with the visit told Reuters.
They spoke on the condition they were not identified as they are not authorised to speak to the media.
Mugabe has a reputation for extensive international travel, including regular medical trips to Singapore - a source of public anger among his impoverished citizens.
(Reporting by Fathin Ungku; Writing by Jack Kim; Editing by Robert Birsel)
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)