By Cris Chinaka
HARARE (Reuters) - Zimbabwe's 90-year-old President Robert Mugabe is in Singapore for "another routine eye check-up", his spokesman said on Thursday, playing down concerns about the health of the veteran African leader who has no obvious successor.
Mugabe had a cataract operation in Singapore on the eve of his 90th birthday in February, officials said, and his visits to the southeastern Asian state have become more frequent over the last couple of years amid fears for his health.
Spokesman George Charamba said Mugabe - who denies he has prostate cancer or any other serious illness - would be away for a week and would undergo a "routine eye check-up following a recent procedure on the same".
When he addressed an independence anniversary rally on April 18, a squinting Mugabe struggled to read his speech and his eyes appeared swollen when he removed his spectacles.
His health is a concern for Zimbabweans who fear instability if Mugabe dies in office without resolving a succession battle raging in his ZANU-PF party, which has ruled the southern African country since independence from Britain in 1980.
Vice-President Joice Mujuru and Justice Minister Emmerson Mnangagwa are seen as the front-runners, but Mugabe, Africa's oldest president, recently confirmed that the contest was open to other ZANU-PF leaders as well.
A June 2008 U.S. diplomatic cable released by WikiLeaks said Mugabe had prostate cancer that had spread to other organs.
He was apparently urged by his physician to step down in 2008 but has remained in the job.
In an interview ahead of his 89th birthday last year Mugabe said he felt he had a "divine task" to lead. He went on to contest and win another five-year presidential term last July that will end in 2018, when he will be 94.
He denies opposition charges that he rigged the election.
Critics say Mugabe, revered in his first decade in power as a liberation hero and pragmatic leader, has clung to power through violence and intimidation and turned one of Africa's most promising economies into a basket case.
He endorsed the seizure of white-owned commercial farms for redistribution to blacks over a decade ago, and has more recently forced foreign firms to surrender majority stakes to locals.
His main rival, Movement for Democratic Change leader Morgan Tsvangirai, is facing a serious internal party challenge after failing to oust Mugabe and ZANU-PF in three elections since 2000.
(Reporting By Cris Chinaka; Editing by Ed Cropley)