Two police officers are among three people who e were Monday killed in a blast in a food kiosk outside Mandera police station.
More than 20 other people were injured in the blast.
An Improvised Explosive Device had been planted in the hotel and was set off as a crowd sat for food, witnesses said.
Suspicions are that the IED had been planted on Sunday night to target those frequenting there.
Among those killed were two police officers and a female civilian.
Police said the woman was the owner of Mama Samaki Hotel which was affected.
The area has been experiencing a lull in attacks from al Shabaab terror group.
Security officials said the bomb was set up by the militants or their remnants operating in the area.
The attack sparked an operation in vain.
Police have been staging operations in the region to downgrade the activities of the terrorists.
On Sunday, at least two members of the National Police Reserve (NPR) were killed in an attack by suspected terrorists in Witu, Lamu County.
Police said another reservist was injured in the attack on Saturday night.
The attackers also burnt a house and a motorcycle before stealing foodstuff.
Witnesses said the victims were shot and killed after a battle.
The survivor had a bullet wound in the leg.
The attack happened in Ziwa la Taa village in Witu, police said.
The attacks have left many dead and displaced hence affecting development.
On Sunday, Kenyan special forces staged an ambush on an al Shabaab temporary camp near the Kenya border past Hagardera refugee camp.
Officials said two al Shabaab fighters were critically injured but managed to escape.
During the successful operation, the team recovered Improvised Explosive Devices (IED) making materials, AK47 riffle, two magazines, porches and assorted foodstuffs.
At least three experts of assembling the explosives managed escape, police said.
The area is near the Kenya- Somalia border where the terrorists cross and launch attacks inland.
A major operation is ongoing in the area to address al-Shabaab-related attacks, which happen because of others, the proximity to the main Kenya-Somalia border.
The area near the border with Somalia has suffered a series of terrorist attacks.
The terrorists have been attacking places near the Kenyan border by using guns and explosives leaving dozens dead and many injured