Kidnappers have escaped into Somalia with an elderly French hostage after a gun battle with Kenyan security forces.
The 66-year-old severely disabled woman was taken from a private house on the island of Manda on Kenya's northern coast yesterday.
It is the second abduction of a foreign visitor in Kenya in the past three weeks.
Britain and France have warned tourists against travelling to the region.
"She's already in Somalia. I can confirm that," Lamu District Commissioner Stephen Ikua said, adding that the Somali Islamist extremist group Shebab was likely behind the kidnapping.
"It must have been Al-Shebab," he said.
A Kenyan government statement earlier said the woman was taken from her home on the archipelago of Lamu in east Kenya by "10 heavily armed Somali bandits," "suspected" to be Shebab.
The kidnapping is the second attack on foreigners in less than one month in this part of Kenya near the border with war-torn Somalia.
The woman, identified by local sources as Marie Dedieu, was taken from her home on Manda island, separated by an idyllic lagoon from the resort isle of Lamu.
The French consulate in Nairobi issued a formal warning to prospective visitors to avoid the archipelago and the region up to the Somali border.
Britain also issued tougher travel advice for Kenya, warning its nationals against all but essential travel to a long stretch of the coast up to the Somali border.
"We advise against all but essential travel to coastal areas within 150km of the Somali border, following two attacks by armed gangs in small boats against beach resorts in the Lamu area," the new travel advice says, according to a foreign ministry statement.
"Beach-front accommodation in that area and boats off the coast are vulnerable."
On 11 September, gunmen attacked a British couple in their fifties - Judith and David Tebbutt - on holiday north of Lamu.
David Tebbutt was shot dead and his wife was captured. She is believed to have been sold to pirates now holding her in central Somalia.
Somalia has been lawless for two decades after plunging into a bloody civil war with the 1991 ousting of president Mohamed Siad Barre.
A Briton kidnapped in southern Somalia in 2008, environmental researcher Murray Watson, is still missing, and a French secret service agent has been held in Somalia for more than two years.
