Mugabe, the country's sole leader since independence from Britain in 1980 and accused by opponents of clinging to power by rigging elections, brought forward his weekly Cabinet meeting to Monday before his departure, officials said.
"The president is going on a private visit for a routine medical checkup – not because he is sick or anything like that, but one consistent with his strong belief in getting regular medical examinations in order to stay healthy," a senior official, who declined to be identified, told Reuters.
Asked why the president was going abroad if it was a routine issue, the official said: "I am not going to be dragged into that kind of malicious debate."
Another official said Mugabe – who addressed a central committee meeting of his Zanu-PF party on Friday – was expected back next week but he refused to discuss any further details.
Mugabe's spokesperson was not available for comment.
Local media reported Mugabe travelled to Singapore eight times last year alone to seek medical attention.
A June 2008 US diplomatic cable released by WikiLeaks last year said Mugabe had prostate cancer that had spread to other organs. His doctor urged him to step down in 2008, according to the cable.
In April, aides angrily denied reports by some international media that he was undergoing intensive treatment in a Singapore hospital and was fighting for his life.
A minister from the rival Movement for Democratic Change (MDC) party who attended Monday's Cabinet meeting said Mugabe did not look sick. "The old man looked his normal old and energetic self, attentive and in control. If he is sick, it was not obvious," the minister said.
Mugabe, one of Africa's longest-serving leaders, has often laughed off suggestions that he is seriously ill, saying he is fit enough to contest an election due in the next year. – Reuters