A man was Sunday injured when suspected Al-Shabaab militants threw a grenade at a group of residents in Garissa Town.
The residents had raised the alarm after two men were spotted behaving suspiciously near a Kenya Power sub-station.
The 8pm incident threw the town into panic as residents scurried for cover after the explosion.
Criminal Investigations Department boss Musa Yego said police were pursuing the suspects and appealed to residents to share any information they might have.
The injured man was rushed to hospital with serious arm injuries.
The attack comes a day after suspected Al-Shabaab gunmen killed a police officer and injured another on Saturday afternoon at Dagahaley in the sprawling Dadaab refugee camp.
The incident will heighten pressure on the Jubilee government to act on runaway insecurity in the country.
Last week gunmen suspected to be members of the terrorist group based in war-torn Somalia executed 28 Kenyans in a Nairobi-bound bus from Mandera town.