Two police officers went missing after more than 50 suspected al Shabaab militants attacked a police base in Garissa on Thursday.
Initial reports had indicated four officers were missing.
National Police Service spokesman George Kinoti said the attackers raided Hamsey police camp at about half past midnight.
Kinoti said they arrived in two Land Cruisers and were repulsed but later returned in a larger number by lorry.
"Officers in the camp managed to repulse them amid fierce exchange of fire,' he said in a statement.
"It was brave of our officers to have managed such a big number of heavily armed attackers."
He said the officers withdrew for cover when some tents were destroyed.
Kinoti said the attackers fired three bombs and shot an officer who was airlifted to Nairobi for further treatment.
He said three others who sustained minor injuries were taken to Dadaab hospital.
The spokesman did not say what the suspected terrorists took but earlier reports indicated they stole guns and a Land Cruiser.
Al Shabaab claimed the attack.
"We attacked a police station in a small town near Garissa last night," al Shabaab spokesman Sheikh Abdiasis Abu Musab told Reuters by phone.
GSU officers were deployed to the area to carry out air and ground surveillance.
Story updated
