The Kenyan air force has said it destroyed two al-Shabab camps in Somalia, in the first major military response since the armed group massacred students at a Kenyan university last week.

Gunmen from the al-Qaeda-aligned group killed 148 people on Thursday when they stormed the Garissa University College campus, some 200km from the Somali border.

Jets pounded the camps in the Gedo region on the other side of the frontier on Sunday and Monday, Kenya Defence Forces spokesman David Obonyo said on Monday. The mission was part of efforts to stop fighters from those camps carrying out cross-border raids into Kenya.

Inside the compound where Garissa massacre took place

"Our aerial images show that the camps were completely destroyed," he said, adding that cloud cover made it difficult to estimate the death toll.

Sheikh Abdiasis Abu Musab, al-Shabab's military operations spokesman, told the Reuters news agency that none of its camps were damaged in Sunday's raid, and that the fighter jets had instead struck farmland.

After besieging the university, the al-Shabab gunmen lined up non-Muslim students before executing them in the armed group's bloodiest attack to date.

The attack claimed the lives of 142 students, three police officers and three soldiers.

President Uhuru Kenyatta on Saturday pledged that the attackers would face justice for the "mindless slaughter" and vowed to retaliate for the killings in the "severest way".

Previous strikes

Monday's air strikes were not the first launched by Kenya against al-Shabab targets.

In June last year, Kenyan fighter jets attacked two bases belonging to al-Shabab fighters in Somalia, killing at least 80 of them, according to African Union (AU) peacekeeping troops deployed there.

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The African Union Mission in Somalia (AMISOM), whose soldiers launched a new offensive against al-Shabab last year, said the Kenyan jets carried out the raids on Anole and Kuday in Somalia's southern Lower Jubba region.

Kenya first sent its troops into neighbouring Somalia in 2011 after several attacks inside its territory that it blamed on al-Shabab. It later joined the AMISOM peacekeeping force.

Al-Shabab has since carried out a string of attacks to punish Kenya for its intervention, including a raid on Nairobi's Westgate shopping mall in September 2013 that killed at least 67 people.

Kenya responded the following November by "completely destroying" an al-Shabab training camp about 300km west of the Somali capital Mogadishu, which was believed to have housed more than 300 al-Shabab recruits.

Source: Al Jazeera and agencies