MANDERA, Kenya, March 14 (Xinhua) -- At least six Kenyan police officers were injured in a roadside explosion in Mandera County in the northeastern part of the country, police confirmed on Saturday.

Police said the blast occurred on Friday after an improvised explosive device (IED) planted by suspected al-Shabaab militants struck a police vehicle along the Elwak-Wargadud Road.

The officers were aboard a police vehicle when it was hit by a directional IED while overtaking a passenger bus heading toward Mandera.

Security agencies have since heightened operations in the area as investigations into the attack continue.

The area is considered vulnerable to the activities of militant groups operating from neighboring Somalia through the porous border. The border region has experienced repeated attacks by the militants, who are at times aided by locals, police said. ■