At least 33 suspected Al-Shabaab terrorists were arrested and two planned attacks foiled in Tana River County between December and March.
Deputy County Commissioner Michael Kioni said that last year, security agencies waylaid some 20 Al-Shabaab terrorists traveling by road to attack Jamhuri Day celebrations in Hola town.
Tana River Governor Hussein Dado and County Commissioner Isaiah Nakoru are said to have been the targets, among other senior county and national governments officials.
He indicated that among the attackers were suicide bombers.
In an interview with the Nation, Mr Kioni said police received prior intelligence that helped them to thwart the attack targeting the crowd attending the public holiday.
He said a team of security officers from the military and Anti-Terrorism Police Unit (ATPU) intercepted the group on the Lamu-Garsen road and seized assorted bomb-making materials.
Mr Kioni said the suspected militants were mainly from Somalia though several of them were Kenyans from various parts of the country.
Two months ago, Mr Kioni said, security agencies thwarted a second Shabaab plan to destroy Safaricom communication masts at the Bura trading centre and arrested 13 attackers, among them a Ugandan.
He said locals have been sensitised to remain vigilant and alert security agencies when they spot suspicious people either on foot or travelling in vehicles.
The county has three main bridges, which are all guarded by police and Kenya Defence Forces (KDF) soldiers.
They include the Mororo bridge, which connects the county to Garissa and has been guarded for decades by police and immigration officers to prevent illegal entry of foreigners into the country.
KDF soldiers are also guarding the Masalani bridge, which connects Tana River to Ijara Sub-County in Garissa and is suspected to be used by terrorists because of its proximity to Boni forest.
Police and the military are also guarding the Garsen bridge in Tana Delta Sub-County that also connects Malindi to Mombasa towns.