Some were hacked to death with knives, others shot and executed at close quarters, mirroring tactics used in earlier attacks claimed by Somalia’s Al-Qaeda-linked Shabaab.
The attack took place overnight on a small village near the town of Witu, on the mainland some 50 kilometres west of the tourist island of Lamu.
Lamu County Commissioner Stephen Ikua called it an “unfortunate attack”, the third in the area this month.
Five bodies were initially found, Ikua said, but a police source later said that six more bodies were found, taking the toll to 11.
READ 5 more killed in attack at Witu, Lamu County
Deputy district commissioner Benson Maisori said that some “were killed with knives”, while others “were shot, executed at very close range.”
Several people were reported to have been wounded in the attack and taken to nearby hospitals for treatment, local councillor Athaman Badi said.
There was no immediate claim of responsibility.
“We have sent our officers to the ground to get more details… they are on the ground pursuing the attackers,” Ikua added.
The village is reported to be a mix of Kenyan ethnic groups.
Attacks last week on the nearby coastal Mpeketoni district left at least 60 dead.
“The style of the attack is very similar to that at Mpeketoni, it seems like it is the same men,” Maisori said.
The flare-up of violence has badly dented Kenya’s tourist industry at one of its traditionally busiest times of the year, a key foreign currency earner and massive employer for the country.
– Attacks stoking ethnic tensions –
Last week’s attacks were claimed by Somalia’s Islamist Shabaab insurgents, though President Uhuru Kenyatta blamed “well-planned, orchestrated and politically motivated ethnic violence” carried out by “local political networks”.
READ Lamu attacks political, not terrorism – Uhuru
President Kenyatta’s accusations have stoked already tense political rivalry between the government and opposition parties, and raised fears of renewed ethnic tension.
After the attacks, Kenyan security forces killed five people they suspected of involvement in the massacres, recovering AK-47 assault rifles as well as ammunition.