NAIROBI (Reuters):

Kenya's first lady slapped a government official during an Independence Day celebration after he introduced her by the name of a woman widely believed to be President Mwai Kibaki's second wife, local media reported.

An official from the president's office made the gaffe introducing Lucy Kibaki to hundreds of guests on Wednesday during a State House garden party.

"Before he could finish, the First Lady rose from her seat at the dais, walked to him and slapped him on the face," the leading Daily Nation said.

Lucy Kibaki was reported to have been incensed when the official acting as master of ceremony introduced her as "Wambui".

Mary Wambui is a woman many Kenyans believe has been Kibaki's second wife for 30 years, despite repeated denials from State House.

"President Kibaki, the Vice-President Moody Awori, several cabinet ministers and members of the diplomatic corps watched in dismay as the drama unfolded," the Standard newspaper said.

A presidential press official said he could not immediately comment. A Daily Nation reporter told Reuters security agents forced the media group's cameraman to erase footage of the incident.

Lucy Kibaki was at the centre of a controversy in 2005 when cameraman Clifford Derrick accused her of slapping him when she stormed into a newsroom to protest her treatment by the media.