The director of Unesco called Friday for a West African dictator to withdraw the controversial prize he has endowed for the organization. The prize in the life sciences, financed by and named for President Teodoro Obiang Nguema Mbasogo of Equatorial Guinea, would damage the “prestige” and “credibility” of Unesco, its director general, Irina Bokova, said at a meeting of the group’s executive board in Paris. Human rights activists, scientists and political leaders have denounced the prize as a public-relations stunt by Mr. Obiang. The Unesco board is expected to meet again next week on the issue.