Kenya Garissa attack by al-Shabaab
Women fall in the dust after a policemen stops a crowd running towards bodies of suspected Garissa University College attackers in a school compound in Garissa Goran Tomasevic/Reuters

Kenya has hit back at terrorist group al-Shabab after last week's horrific massacre at Garissa University that left 148 students dead.

The air strikes hit two training camps in the south of Somalia that Kenyan authorities believe were being used as staging posts to attack Kenya.

They come as more information has surfaced about the men who carried out the killings, which shocked Kenya and the wider world last week as stories emerged of gunmen separating Christian and Muslim students before killing the former.

This includes details about Abdirahim Mohamed Abdullahi, a so-called model student and aspiring law graduate and government official's son that turned to militant Islam.

"We targeted the two areas because according to the information we have (those al-Shabab) fellows are coming from there to attack Kenya," a military spokesman told Reuters.

'Severe' retribution

President Uhuru Kenyatta said last week that the country would respond in "the severest way possible" to the attack, one of a number Islamist atrocities to hit Kenya since it joined an African Union effort to push the group out of Somalia.

These included 2013's Westgate shopping mall attack, when 63 civilians were killed after four men went on a rampage in a popular Nairobi shopping centre.

These has been criticism of the government's response over Garissa in recent days, with CNN quoting anonymous sources that said Kenya's rapid response team was delayed in Nairobi for several hours before being dispatched to the city.

Al-Shabab had previously controlled most of Somalia and at one point its previous incarnation, known as the Islamic Courts Union, seized the capital Mogadishu.

The African Union Mission in Somalia (AMISOM) has forced al-Shabab out of the capital and into the countryside, but that push south has seen them cross the porous border with Kenya and carry out attacks.