Robert Mugabe is reportedly fighting for his life in a hospital in Singapore, although a party official said he is simply on his "Easter holidays".
An unnamed senior Zanu-PF official told the Zimbabwe Mail the president is undergoing intensive treatment in Singapore and his family have boarded a chartered plane to join him.
Mugabe reportedly collapsed in his home last week.
The 88-year-old is believed to be suffering from prostate cancer, according to a 2008 US diplomatic cable leaked by Wikileaks.
However a second party official denied Mugabe had a health emergency, and was to return to the country on Wednesday after holidaying with his family.
"The President is on his Easter holidays, like everyone else," he told the Mail.
"He returns to his post this week, at the same time as those who are asking about his whereabouts from their holiday hideouts."
Another spokesperson for the president told the paper Mugabe had flown to Singapore to help his daughter Bona with her application for post-graduate studies.
Mugabe's health issues have caused concerns for the country's coalition government, which was formed between Zanu-PF and Prime Minister Morgan Tsvangirai's MDC-T after a disputed election in 2008.
Zanu-PF, which is trailing in polls according to the Mail, may be forced to call an early election should the party leader's health deteriorate further.
With no strong alternative leader in the party, it is feared the military could attempt to take over the country.
The next election is to be held next year.
MDC-T is dismayed a meeting last week to discuss the Indigenisation and Economic Empowerment Policy, which MDC-T claims undermines investor confidence and is stifling the economically-crippled country's recovery, was called off after Zanu-PF politicians snubbed the meeting as Tsvangirai was to chair it in Mugabe's absence.
Mugabe's absence has also resulted in the postponement of cabinet meetings.
Mugabe has ruled Zimbabwe since independence from Britain in 1980.