A coalition of human rights groups has condemned a UN agency for planning to award a prize sponsored by Equatorial Guinea President Teodor Obiang Nguema.
The 28 groups say Unesco should end its association with "one of the world’s most infamous dictators".
Mr Obiang, who has led the oil-rich country for 30 years, has been accused of rigging elections and corruption. He has previously denied such charges.
The first $3m (£2m) Unesco-Obiang science prize is to be awarded in June.
A Unesco spokesperson told the BBC the agency had no comment to make because the decision had been approved by the organisation’s board in April.
Mr Obiang seized power from his uncle in 1979. He was re-elected last year with 95% of the vote.
Last year, a French court threw out a lawsuit against Mr Obiang and two other African leaders, accusing them of using public funds to buy luxury homes.
The court said foreign heads of state could not be sued.
The human rights coalition has written to Unesco, asking it to identify the source of the funds used to sponsor the prize.
"The prize’s $3m endowment should be used for the education and welfare of the people of Equatorial Guinea, rather than the glorification of their president," said Tutu Alicante of the human rights organization EG Justice.
Equatorial Guinea’s vast earnings from oil and gas should give its population of 600,000 people a theoretical income of $37,000 a year each.
But most Equatorial Guineans live in poverty after 15 years of plentiful oil production.
Human Rights Watch describes Equatorial Guinea’s government as one of the most abusive and corrupt in the world.
"The grim irony of awarding a prize recognizing ‘scientific achievements that improve the quality of human life,’ while naming it for a president whose 30-year rule has been marked by the brutal poverty and fear of his people and a global reputation for governmental corruption, would bring shame on Unesco," reads the letter.
Normally a secretive state, Equatorial Guinea made headlines in October with the pardoning of a group South African and British mercenaries headed by Simon Mann who had been jailed for attempting a coup.
In 2004, a US Senate investigation discovered that Mr Obiang, and members of his family, were the signatories to accounts at Riggs Bank in the US which had received millions of dollars in revenues from the central African country’s oil wells.
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