Kenya warplanes strike Shebab camps in Somalia: Army

"We bombed two Shebab camps in the Gedo region," Kenyan army spokesman David Obonyo told AFP.

"The two targets were hit and taken out, the two camps are destroyed."

The airstrikes follow threats by President Uhuru Kenyatta that he would retaliate "in the severest way possible" against the Shebab militants for their attack on Thursday on a university in Kenya's northeastern town of Garissa in which nearly 150 died.

There was no information given as to casualties in the bases hit.

The Shebab gunmen launched the pre-dawn attack in Garissa, storming dormitory buildings before lining up non-Muslim students for execution in what Kenyatta described as a "barbaric medieval slaughter".

The massacre, Kenya's deadliest attack since the 1998 bombing of the US embassy in Nairobi, claimed the lives of 142 students, three police officers and three soldiers.

Kenyan airplanes have made repeated strikes in southern Somalia since their troops crossed into their war-torn neighbour in 2011 to attack Shebab bases, with Nairobi later joining the African Union force fighting the Islamists.

"The bombings are part of the continued process and engagement against Al-Shebab, which will go on," Obonyo added.

The Shebab fled their power base in Somalia's capital Mogadishu in 2011, and continue to battle the AU force, AMISOM, sent to drive them out that includes troops from Burundi, Djibouti, Ethiopia, Kenya and Uganda.

The group has carried out a string of revenge attacks in neighbouring countries, notably Kenya and Uganda, in response to their participation in the AU force.

On Saturday, Shebab warned of a "long, gruesome war" unless Kenya withdrew its troops from Somalia, and threatened "another bloodbath".

Shebab fighters also carried out the Westgate shopping mall attack in Nairobi in September 2013, a four-day siege which left at least 67 people dead.

Five men have also been arrested in connection with the university attack, including three alleged "coordinators" captured as they fled towards Somalia, and two others in the university.