Kenyan security agents seized and erased a video showing the first lady slapping a government official, apparently angered because he introduced her by the name of a woman widely believed to be the president's second wife, officials said Friday.

Kenya's media regulator gave President Mwai Kibaki's office two weeks to explain the incident, which happened at the president's official residence during Wednesday's Independence Day celebration. The deadline means no response is due until after the Dec. 27 presidential election, in which polls show Mwai Kibaki is trailing and which is shaping up to be the closest in Kenyan history.

"We don't want to pre-empt anything but the complaint is a gross violation of press freedom," said Wachira Waruru, the chairman of the Media Council of Kenya.

The complaint was lodged by Kenya's largest media house, the Nation Media Group. The Nation said security agents erased photo and television images of Lucy Kibaki slapping the government official after he called her "Wambui" — the name of a woman many Kenyans believe has been Kibaki's second wife for 30 years. Kibaki has denied he has a second wife.

In a newspaper interview later, the official said he had slipped, introducing Lucy Kibaki as "Lucy Wambui."

In May 2005, Lucy Kibaki stormed into the newsroom of the Daily Nation, Kenya's largest newspaper, with her security detail demanding journalists be arrested for what she considered biased coverage. A journalist sued her for assault, but a court dropped the charges because Attorney General Amos Wako said the police nor prosecutors had had time to investigate whether she had slapped the journalist.