Kenyan fighter jets pounded Al-Qaeda-linked Shebab insurgent camps in southern Somalia on Monday, the army said, days after the militants killed 148 people in their worst ever massacre in Kenya.

Kenyan fighter jets pounded Al-Qaeda-linked Shebab insurgent camps in southern Somalia on Monday, the army said, days after the militants killed 148 people in their worst ever massacre in Kenya.

The airstrikes, which the army said destroyed two Shebab bases, came on the second day of national mourning in Kenya, and as security forces tried to hunt down those behind the university killings.

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.

The airstrikes followed a promise by President Uhuru Kenyatta that he would retaliate "in the severest way possible" against the Shebab militants for their attack last Thursday.

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