Zimbabwe's 86-year-old President Robert Mugabe denies having been gravely ill and describes reports that he recently underwent surgery in Malaysia as "naked lies crafted by the Western-manipulated media," state radio reported Monday.

Mugabe arrived home late Sunday from his annual vacation and said he had been in Singapore, not Malaysia. Reports in the British, South African and independent Zimbabwean media said Mugabe was operated on for an inflamed prostate gland, citing diplomats and other unnamed sources.

Mugabe, who is scheduled to attend an African Union summit in Ethiopia later this week, told the fiercely loyal state broadcaster that there were always Western-sponsored rumors he was dying when he was absent from his office.

"Those are the lies they put across from year to year. Now it's something you expect each time I go on leave and they also go on their campaigns," he was quoted as saying.

Mugabe has ruled Zimbabwe for 30 years and has long fended off challenges to his leadership, but now is believed by many to be losing his grip on factions in his party.

Finance Minister Tendai Biti, a top aide to the country's longtime opposition leader who is now prime minister, told supporters at a party rally in December that Mugabe fell asleep during a two-hour meeting they had to discuss his 2011 budget proposals.

Mugabe's public speeches have become noticeably shorter and government ministers of the former opposition say the ascetic and intellectual one-time school teacher recently has become prone to losing his concentration at ministerial meetings.

Mugabe said there were members of his party "jostling" to be his successor as Zimbabwe heads toward elections proposed for later this year.

He told the broadcaster that he had the constitutional power to call the elections this year even if electoral and constitutional reforms are not complete, saying his power-sharing coalition with Prime Minister Morgan Tsvangirai "was not meant to be a permanent arrangement."

"I can invoke the existing constitution and call elections," he said, according to state radio.

The coalition was formed after disputed violence-plagued elections in 2008. Tsvangirai's party won the parliamentary vote but he boycotted a presidential run off poll to protest violence against his supporters by Mugabe militants and loyalists in the police and military.

Independent poll monitors and human rights groups say a program to rewrite the constitution last year through countrywide public meetings was also marred by violence blamed mostly on Mugabe militants who are still in place in bases across the country.