In June 2004, on returning from yet another extended stay abroad, Cameroon President Paul Biya came down from his plane and poked fun at rumours he was dead.

"People are interested in my funeral," he told reporters. "I'll see them in 20 years."

That was 21 years ago, and the world's oldest serving head of state still has no plans to go anywhere.

On Sunday, he announced on X that he would run in Cameroon's presidential election scheduled for October 12, seeking an eighth term that could keep him in office until he is nearly 100.

Biya has held a tight grip on power since taking over as president in 1982 from his one-time mentor Ahmadou Ahidjo, whom he later sidelined and forced into exile.

Now, an unprecedented public outcry in the press and on social media since his announcement suggests cracks in that power base, and doubts in his ability to keep going, may be growing.

"Nous sommes foutus" ("We are screwed!") was the front-page headline in Monday's edition of Le Messager newspaper next to a picture of Biya.

The cocoa- and oil-producing Central African nation faces a host of economic and security challenges, notably a conflict with Anglophone separatists and threats from Nigeria-based Islamist fighters in the north.

Meanwhile, Biya, 92, remains largely out of public view, spurring widespread speculation over who is really in charge.

"Most of us don't believe Biya is actually running the country anymore. His decision to run again, if it's really his, shows just how out of touch the system is," tech entrepreneur Rebecca Enonchong told Reuters.

Communications Minister Rene Emmanuel Sadi did not immediately respond to a request for comment on Monday. He has previously said Biya is in good health and that speculation to the contrary was "pure fantasy and imagination" by critics aiming to destabilise the country.

Last year, the government banned public discussion of Biya's health - though that order has been largely ignored by Cameroon's vociferous press.

CALLS TO STEP ASIDE

Cameroon has had just two presidents since independence from France and Britain in the early 1960s and is likely to face a messy succession crisis if Biya becomes too ill to remain in office or dies.

In 2008, Biya signed a constitutional amendment removing a two-term limit for the presidency.

That paved the way for landslide wins in 2011 and 2018, according to official figures, though his opponents complained of irregularities including ballot stuffing and intimidation, which the government denied.

Not much has changed since the last vote, both on the security front and for Cameroonians grappling daily with poor access to basic amenities, from roads and water to electricity and waste management.

"These issues are not new. They have simply intensified because the situation keeps worsening," said Pippie Hugues Marcelline, research policy analyst at the Yaounde-based Nkafu Policy Institute, a think tank.

What is different this year, Marcelline said, is "the level of engagement and awareness" about Biya's performance.

"A president needs to be seen in charge and in control. The absence of the president from the public is enough evidence that age is not on his side."

Prominent human rights lawyer Alice Nkom published a video last week on YouTube appealing to Biya to step aside.

"The legs are no longer holding up, the brain is no longer working. I'm telling you this because I'm in this situation, because I'm in my 80s," she said.

"I know what has changed in me and what I can no longer give to Cameroonians."

Perhaps more worrying for Biya, two former allies have recently quit the ruling coalition and announced plans to run in the election separately.

Enonchong, the tech entrepreneur, told Reuters she did not think Cameroonians would accept another Biya term.

But analyst Raoul Sumo Tayo said that, despite the many obstacles, Biya should not be counted out.

"The ruling party can successfully rally the administrative elite and utilise outdated electoral practices," he said, referring to what he described as fraudulent tactics.

"It might just secure an eighth term for Paul Biya."