DAKAR/ATHENS (Reuters) - Gunmen kidnapped seven French nationals, including three children, on Tuesday in northern Cameroon near the border with Nigeria and the perpetrators came from neighboring Nigeria, French President Francois Hollande said. The risk of attacks on French nationals and interests in Africa has risen since France sent forces into Mali last month to help oust Islamist rebels occupying the country's north. "They have been taken by a terrorist group that we know and that is in Nigeria," Hollande told reporters during a visit to Greece. ...