The Kenyan government has intensified its search for a kidnapped British woman whose husband was killed at a luxury resort near the Somali border.

Authorities said they were using all available resources to find the missing woman. Police and soldiers searched the border area on Monday using helicopters and speedboats.

Investigators said armed men attacked David and Judith Tebbutt early Sunday, just hours after they checked into the Kiwayu Safari Village on Kiwayu Island, north of Lamu Island. They were the only guests at the time.

Officials say the assailants fatally shot the husband in the couple's cottage and then carried the woman to a motorboat and sped away.

There was no immediate claim of responsibility for the murder and abduction.

Police say they suspect al-Shabab militants in Somalia may have launched a cross-border crime.

Britain Foreign Office had advised its nationals not to go within 30 kilometers of the Kenya-Somalia border.

The couple, both believed to be in their 50s, are from Bishop's Stortford, Hertfordshire, England.