A corruption investigation in Gabon has revealed the existence of about 3,000 fake civil servants who receive monthly government salaries despite holding no official positions, officials said.

The oil-rich Central African nation's bloated civil service employs about 70,000 workers and serves a population of 1.5 million.

"The beneficiaries regularly received monthly salaries despite not belonging to any ministry," State Prosecutor Sidonie Flore Ouwe said on Wednesday.

"We have already seized some of them with counterfeit diplomas and fake assignments," she said, adding that those involved in the scam would be prosecuted. Some suspects had been arrested, Ouwe added.

"This mafia-like network has branches in higher education establishments and in some administrations," said Maurice Ekogha, an advisor at Gabon's Budget Ministry.

The government had estimated that there were up to 10,000 fraudulent state employees, which cost Gabon about 25 billion CFA francs ($50.3m) in salaries every year.

In 2009, it launched an overhaul of the civil service and fired 800 employees. Another 2,500 were questioned on suspicion of illegally receiving multiple government salaries.

Although its oil resources and small population give it one of Africa's highest per capita income levels, wealth in Gabon is unevenly distributed.