CAIRO - Egyptian authorities have denied permission to eight U.S.-based nonprofit groups to operate locally, including a center headed by former U.S. President Jimmy Carter that monitors elections, a ministry official said Monday.

The Social Affairs Ministry official said the licenses were denied because the groups' activities "breach the country's sovereignty." He did not elaborate. He spoke Monday on condition of anonymity because he was not authorized to brief the media.

The move comes only a month ahead of presidential elections slated for May 23, the first since the ouster of longtime authoritarian leader Hosni Mubarak 14 months ago.

Sanne van den Bergh, who heads the Carter Center in Egypt, said the group has not yet received formal notification of the decision. Observers from the center were allowed by the country's military rulers to "witness" multistage parliamentary elections that ran November to February. The Carter Center said the vote was generally fair.

A recent criminal investigation into alleged violations by U.S.-based nonprofit groups in Egypt led to the worst diplomatic row between Cairo and Washington in three decades. American employees were referred to trial on charges that they had used illegally obtained funds to promote activities that undermined stability.

Most of the Americans were out of the country when investigative judges referred them to trial and those who stayed behind were later allowed to leave.

The Carter Center is the most prominent of the eight groups. Some of the others are linked to U.S.-based churches.