The arrests appear to signal a heightened campaign by the government of President Mahamadou Issoufou, who said at his inauguration to a second term on April 2 that his main priority was to step the fight against corruption.
"Eight officers in the public service and health ministries were charged and jailed for acts of corruption, examination fraud and criminal association," said prosecutor Samna Chaibou, adding that the results of the exams had been annulled.
"The facts are extremely serious especially because they concern the health sector. Imagine 1,831 people entering the sector who have zero qualifications," Chaibou said on Tuesday, adding that 14,000 people had applied for the jobs.
Civil service jobs are seen as relatively lucrative and stable in Africa, where many people lack formal employment. As a result, competition for entry into government bureaucracy can be intense, which can lead to corruption.
Transparency International ranked Niger in 99th place in 2015 in its annual listing of countries according to perceptions of corruption, up from 134th place in 2010.