The organisation said nine people had died and one person was missing in the locality of Gamba, while four people had been killed in Hindi, a trading post near Lamu island. The areas were attacked yesterday, authorities said.
There were no further details from officials on the attacks, with Kenya's National Disaster Operations Centre only saying in a brief statement on Twitter yesterday that gunfire had broken out.
"The attackers came back home safely to their base," Shebab military spokesman Abdulaziz Abu Musab said, saying that 10 people had been killed in the attack.
The Shebab also claimed responsibility for last month's attack at Mpeketoni, saying it was in retaliation for Kenya's military presence in Somalia as part of the African Union force backing the country's fragile and internationally-backed government.
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Survivors of the massacre in Mpeketoni and a similar attack the following night in a nearby village reported how gunmen speaking Somali and carrying Shebab flags killed non-Muslims and said their actions were revenge for Kenya's presence in Somalia.
The had attackers appeared to target Mpeketoni because the town is a mainly Christian settlement in the Muslim-majority coastal region, having been settled decades ago by the Kikuyu people from central Kenya, the same tribe as Kenyatta.
Police also arrested alleged separatists from the Mombasa Republican Council, a group that campaigns for independence of the coastal region, as well as the governor of Lamu county, who is an opposition politician.