London (CNN) -- One British citizen was killed and another one was kidnapped overnight at a resort near Kenya's border with Somalia, Britain's Foreign Office told CNN Sunday.
The attack occurred at a beach resort north of Lamu, Kenya, the foreign office said.
A maritime security source aware of the situation said the victims were a couple and the husband was killed. His wife has likely been taken by Islamic militants by boat toward Ras Kamboni in Somalia, the source told CNN.
"We are working to secure the safe and swift release of the British national who has been kidnapped and ask those involved to show compassion and release the individual immediately," the foreign office said in a statement.
British officials did not release further details about the kidnapping case, but said they are working closely with Kenyan authorities.
The office said it has amended its travel advice for Kenya in light of the attack.
"We continue to advise against all but essential travel to within 30 kilometers of Kenya's border with Somalia. There have been previous attacks by Somali militia into Kenya," the advisory said.
CNN's David Wilkinson contributed to this report.