Armed men have killed one British national and kidnapped a second one in northern Kenya, near the border with Somalia.

Britain's Foreign Office said Sunday the attack occurred at a resort north of Lamu, an island off the Kenyan coast.

It later sent out an advisory advising against all but essential travel to within 30 kilometers of the Kenyan-Somali border.

Details on the incident are sketchy, but Kenyan police now suspect members of the Islamist group al-Shebab may have been behind the attack, rather than pirates as originally thought. There has been no claim of responsibility. Neither British nor Kenyan officials have identified the victims.