An Ethiopian court has jailed a blogger for 18 years and five other exiled journalists for terms ranging from eight years to life behind bars for plotting with rebels to overthrow the government.

Dissident writer Eskinder Nega was one of 24 Ethiopians who were convicted last month of conspiring with rebels to topple the government.

As the third case in six months involving members of the media, the crackdown has raised fresh concerns over the East African nation's approach to press freedom and human rights.

"The court has given due considerations to the charges and the sentences are appropriate," Judge Endeshaw Adane said.