Kenyan fighter jets have bombed positions of militant Islamist group al-Shabab in neighbouring Somalia, a military spokesman has told the BBC.

The warplanes had targeted two camps in the Gedo region, used by al-Shabab to cross into Kenya, the spokesman added.

This is Kenya's first response to an al-Shabab assault which left 148 people dead at Garissa University last week.

President Uhuru Kenyatta had vowed to respond to the attack "in the severest way possible".

Kenyan army spokesman David Obonyo told the BBC that the military had responded to "threats" by launching the air strike on Sunday night in the remote region.

No further details of the operation were available at this stage, he said.

Two camps had been destroyed, he said, adding: "The bombings are part of the continued process and engagement against al-Shabab, which will go on."

The attack on Garissa University, about 150km (90 miles) from the Somali border, was the deadliest by al-Shabab in Kenya.

The al-Qaeda affiliate says it is at war with Kenya, and wants it to withdraw troops sent to Somalia in 2011 to help the weak government in Mogadishu fight the militants.

'Charming fellow'

Governors and MPs from north-eastern Kenya have called for the closure of the Dadaab refugee camp, where about 500,000 people who fled conflict in Somalia are taking shelter.

They told a news conference in the capital, Nairobi, that the camp was used by al-Shabab as a training and coordination centre.

Aid agencies have rejected previous calls for the closure of Dadaab, the largest refugee camp in Africa.

An MP in Garissa, Aden Duale, said Kenya should "engage" with the international community to step up patrols along its long and porous border with Somalia.

Meanwhile, Kenya's government has denied accusations that its security forces were slow to respond to Thursday's assault on the university.

Mr Kenyatta's spokesman Manoah Espisu told the BBC that the military was at the scene within minutes of the attack, and had helped save the lives of many students on campus.

Local media reported that it took special forces several hours to arrive at the university because of delays in their flight from Nairobi.

The attack ended when the four militants were killed by police more than 15 hours after they stormed the university.

One of the gunmen has been named as Abdirahim Abdullahi, a law student who graduated from Nairobi University in 2013.

His father is a local chief, and had reported his son missing, according to local media.

A former fellow student of Abdullahi told BBC Newsday that he had been a "charming fellow" who did not show any sign of holding militant views at university.

"He was very intelligent... I was very shocked that a person I sat with in class - what would drive someone to change so much?" said the former student, who asked not to be identified for fear of reprisals.