Cameroonian President Paul Biya ordered tight security measures and urgent steps to free the hostages, who include four children. They were kidnapped by armed gunmen in the country's far north on Tuesday and whisked across the nearby border to Nigeria. A ministry statement said the Cameroonian government is in contact with Nigerian and French authorities.
Officials suggested the involvement of Boko Haram, one of Nigeria's Islamic extremist sects.
The kidnapping came as thousands of French troops are deeply involved in a military intervention against Islamic extremists who had taken control of a big part of the West African country of Mali.
French President Francois Hollande, speaking at a Cabinet meeting Wednesday, called it an "odious act" and expressed particular horror that children were involved, according to his government spokeswoman.
France's defense minister said Wednesday that there was no proven link between the French operation in Mali and the Cameroon kidnapping. But, speaking on France-2 television, Jean-Yves Le Drian said: "These are groups who adhere to the same fundamentalism and who have the same methods, whether it is in Mali, in Somalia or in Nigeria, who want to create a lawless zone" stretching from the Atlantic across the southern edge of the Sahara to Sudan.
France's government warned French citizens to avoid travel in northern Cameroon after the kidnapping and urged anyone currently there to leave immediately.
French Foreign Ministry spokesman Philippe Lalliot, in an online exchange with reporters Wednesday, said that in northern Cameroon, "There was never a security incident linked to terrorism; Nigerian terrorist groups had never carried out actions in this part of Cameroon."
A Cameroonian government official said military helicopters were being used in the search.
Cameroon state television cited government sources in the locality saying that the three adults have been separated from the four children.
The family was on tour at the Waza National Park in Cameroon's Far-North Region before they were abducted at gunpoint by five gunmen aboard motorbikes, according to paramilitary sources in the area.
A Cameroon government statement late Tuesday night said the hostages were abducted at Sabongari, seven kilometers from Dabanga, which flanks Cameroon's frontier with Nigeria. The statement did not say whether the Cameroon government is in contact with the kidnappers.
Angela Charlton in Paris contributed to this report.
Copyright 2013 The Associated Press.