The African president has his hands firmly on the reins of government at home and is frequently on the move, flying around the globe.

At age 91, Zimbabwe's President Robert Mugabe shows few signs of slowing down amid periodic speculation about whether he is ill or in decline.

Cabinet ministers from both his party and the opposition who have worked with him say he pays immense attention to detail regarding policies, laws and the national budget. During negotiations ahead of a new constitution in 2013, Mugabe sat with his party's key leaders for as long as 10 hours, scouring through each clause.

This weekend, he will preside as chairman of the African Union over a meeting in Johannesburg of leaders from around the continent. The talks could focus on political unrest in Burundi, the Boko Haram insurgency in Nigeria and African migrants fleeing conflict.

The selection of Mugabe as head for one year of the 54-member African Union strikes some as a poor precedent on a continent where democratic change has struggled for a foothold in many regions. Mugabe is also the rotating chief of the Southern African Development Community, a 15-nation group.

"It sends a very bad message in terms of peaceful transfer of power," said Muna Ndulo, a law professor and head of the Institute for African Development at Cornell University in America.

Africa's oldest leader, Mugabe is a resilient, sometimes ruthless operator who fought in a guerrilla war, denounces the West, crushed or co-opted dissent at home and has been in power for 35 years with no clear successor.

This weekend's gathering in South Africa will follow more than a dozen international trips that Mugabe has made this year, including to Russia to mark the 70th anniversary of the World War II victory over Nazi Germany and most recently to Egypt for a trade conference. In public, the frequent flyer looks dapper in a suit and tie and often shows a wry sense of humor, though observers say his speeches tend to be shorter than in the past, which suggests he is slowing down a tad.

Only President Jose Eduardo dos Santos of Angola and President Teodoro Obiang Nguema of Equatorial Guinea have ruled longer than Mugabe in Africa.

On a trip to South Africa earlier this year, Mugabe mixed statesmanship with self-deprecating humor at a news conference, calling for a "political environment of freedom" that allows Africans to be "masters of ourselves" and thanking journalists "who focused on me as a real dictator" for giving him publicity.

"The gift of politicians is never to stop speaking until the people say, 'Ah, we are tired,'" Mugabe said in closing. "You are now tired. I say, thank you."

Mugabe's extraordinary longevity is, needless to say, discouraging to long-suffering opposition figures who blame him for Zimbabwe's economic dive and what they call a flagrant disregard for human rights. He became leader after independence from white minority rule in 1980 and was re-elected as president in 2013 in a disputed vote that highlighted opposition disarray. Under Zimbabwe's new constitution, he can serve a maximum of two five-year terms, theoretically making him eligible to rule until 2023.

Mfundo Mlilo, spokesman for the Crisis in Zimbabwe Coalition, a group that seeks change in Zimbabwe, lamented a kind of fatigue among many Zimbabweans, saying the message that Mugabe must resign "somehow got lost" in the past decade and that few people respond to calls for street protests. He anticipates, however, that economic hardship will drive popular discontent.

In one possible flashpoint, Zimbabwe's government has threatened to evict vendors who can't get formal employment from the streets of major towns. Some vow they'll stay despite the order.

Still, Mugabe's ZANU-PF party remains dominant, sweeping parliamentary by-elections in 16 constituencies on Wednesday. Major opposition parties boycotted the vote, saying a lack of electoral reforms favored the ruling party, which has been rocked by internal purges seen as the early stages of a battle by rival factions to succeed Mugabe. The president has two vice presidents, including longtime aide Emmerson Mnangagwa; a previous deputy, Joice Mujuru, was fired after being accused of plotting to assassinate Mugabe.

The president has traveled to Singapore in recent years for medical care, and in February, he tripped at the Harare airport after returning from Ethiopia, triggering fresh speculation about his health as well as Internet memes that depicted his falling pose on a dancehall stage, a running track and plunging in a waterfall.

Yet Mugabe was soon on the road again.