Kenyan security forces have killed 10 suspected al Shabaab Islamist militants and arrested 36 others in nine months since launching an operation against the insurgents at the Coast, the head of the operation said on Friday.

Somalia's al Shabaab have claimed a series of attacks in the past three years or so in Kenya that have killed hundreds of people. Several raids targeted coastal sites, and Kenyan officers say they have been launched from Boni forest hideouts.

James Ole Serian, head of the joint army and police operation, said troops had swept the forest and destroyed hideouts used by the militants, who say they target Kenya for sending troops into Somalia with an African force fighting al Shabaab there.

READ: Kenya plans offensive against Islamist militants in coastal forest

"We are having a permanent base set up within the forest that will be used by both our military and police to ensure continuous security," he told Reuters, adding that "around 10" suspected militants who refused to surrender had been killed.

In addition, he said at least 36 had been detained.

Kenya also said on Monday it was drawing up a timetable to close Dadaab camp, home to about 350,000 Somali refugees, citing concerns it was being used by militants. The United Nations, the United States and rights groups have urged Kenya to reconsider.

READ: Kenya draws time plan to close refugee camp for Somalis

In 2014, about 100 people were killed by al Shabaab militants in the Mpeketoni area of Lamu County, next to Boni forest.

Last year, Ole Serian said they had destroyed five al Shabaab hideouts in the forest and recovered a cache of arms.

Kenya has beefed up security in Lamu County and Lamu town, a popular tourist destination where visitor numbers in the wake of the militant attacks. Lamu lies near the Somali border.