The latest attack by the Al Qaeda linked Al Shabaab occurred at a restaurant and a shop in the town.
“We are investigating the incident. No suspect has been arrested so far, but we are told they threw the grenades and fled,” North Eastern Provincial police Chief Philip Tuimur said.
Tuimur said more officers had been deployed to patrol the region to keep the attackers away.
Security forces have become increasingly targeted by the terrorists, mainly at the border towns. Some of the attacks have also occurred in Nairobi.
Nairobi Provincial Police commander Anthony Kibuchi has urged members of the public to remain vigilant and volunteer any information to authorities.
“Al Shabaab is still issuing threats to cause massive destruction in the city; let us remain extra vigilant,” Kibuchi said.
Nairobi, Mombasa and towns in North Eastern Province have suffered deadly attacks since late last year, resulting in dozens of deaths and injuries.
The latest deadly attack occurred in Garissa three weeks ago when suspected militants opened fire and hurled grenades inside two churches, killing 18 people.
More than 60 others were wounded in the attacks.
On Monday, a police officer was killed and his colleague wounded when they were ambushed by people believed to be Al Shabaab militants in Lagdera.
The attack occurred when their vehicle was sprayed with bullets.
Just last week, two police officers were shot and seriously wounded in Mandera in another attack blamed on Al Shabaab militiamen.
The officers who were in a group of three were heading back to Garissa when the militants attacked them in Arabia area, a few kilometres from the border with Somalia.