From Obiang to Putin: longest-serving heads of state

Equatorial Guinea's President Teodoro Obiang Nguema Mbasogo, who is seeking a sixth term in elections on Sunday, is the world's longest-serving president, having spent 43 years in power.

Here are the other longest-serving non-royal heads of state.

40 years

Four decades in power: Cameroon's President Paul Biya. By Ludovic MARIN (AFP/File)

Cameroon has lived through 40 years of the largely unchallenged hardline rule of President Paul Biya, the world's oldest head of state at 89.

Openly talking about succession is taboo even for his closest supporters, and Biya has overseen a ruthless crackdown on dissent since his highly contested re-election in 2018.

30 years and over

In Congo-Brazzaville, Denis Sassou Nguesso has been in power for 38 years, albeit not uninterruptedly. He was president from 1979 to 1992, then returned to office in 1997 after a civil war and remained in charge ever since, changing the constitution to allow him to seek a fourth term in March.

Asian strongman: Cambodia's Prime Minister Hun Sen. By Tang Chhin Sothy, TANG CHHIN SOTHY (AFP)

In Cambodia, strongman ruler Hun Sen has ruled the kingdom for 37 years, making him Asia's longest-serving leader.

Uganda's Yoweri Museveni has led the central African country for 36 years, and was re-elected to a contested sixth term in 2021.

Iran's Ayatollah Ali Khamenei has been supreme leader of the Islamic republic since the death of Ayatollah Khomeini 33 years ago.

And Tajikistan's Emomali Rakhmon, a former collective farm boss who came to power shortly after the collapse of the Soviet Union, has had a firm grip on his poor, mountainous country for 30 years.

20 years and over

Former rebel leader Isaias Afwerki has been president of the Horn of Africa nation of Eritrea for 29 years, since independence in May 1993.

Belarus President Alexander Lukashenko, another former collective farm boss, has used Soviet-style repression to remain in power in Ukraine's neighbour for 28 years.

Djibouti's President Ismail Omar Guelleh, who was re-elected to a fifth term last year, has been leader of the small maritime hub, which styles itself the "Dubai of Africa", for 23 years.

Also totalling 23 years to date is Russian President Vladimir Putin.

Twenty-three years in power: Russian President Vladimir Putin. By Mikhail Metzel (SPUTNIK/AFP)

Putin became prime minister in August 1999, then president the following year and served two terms before swapping jobs with prime minister Dmitry Medvedev in 2008, only to reclaim the role of Kremlin leader in 2012. He was re-elected in 2018.

Rwandan President Paul Kagame, leader of the rebel force that ended the country's 1994 genocide, has been in power for 22 years. In 2015 he changed the constitution to allow him potentially to rule until 2034.