Ethiopia's Supreme Court sentenced an exiled former president — dictator Mengistu Haile Mariam — and 18 officials to death Monday, a prosecutor said.

Yoseph Kiros said the judgment delivered justice for the thousands of people murdered during Mengistu's 17-year rule.

"I believe it is the right verdict because these people committed serious crimes against humanity," Kiros said.

Mengistu, a Marxist leader who was driven from power in 1991 by the current regime, is living in comfortable exile in Zimbabwe and is not expected to be extradited while Robert Mugabe remains Zimbabwean president.

A runoff in Zimbabwe's presidential race is scheduled for June 27. Mugabe's opponents say he is using violence and intimidation in an attempt to win the runoff and retain power. Nevertheless, opposition leader Morgan Tsvangirai has said he is confident of victory.

The 18 other officials sentenced to death Monday are all in Ethiopian custody.

Some experts say 150,000 university students, intellectuals and politicians were killed in a nationwide purge by Mengistu's regime, though no one knows for sure how many suspected opponents were killed.

Human Rights Watch has described the 1977-78 campaign known as the Red Terror as "one of the most systematic uses of mass murder by a state ever witnessed in Africa."

Mengistu had previously been sentenced to life imprisonment in January 2007 for genocide, but the prosecution appealed the sentence in July as unduly lenient.

Under Ethiopian law, the current president must approve the death sentences before an execution date is set.