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 the 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 strikes on Sunday night in the remote region.
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."
But an eyewitness, speaking to BBC Somali, said the attack had wounded three civilians, and destroyed livestock and wells in an area without an al-Shabab presence.
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.
Analysis: Abdullahi Abdi, BBC Africa, Nairobi
This is the latest in a series of air strikes that Kenya's military has carried out in Somalia. Often, they are accompanied by reports of civilian casualties - in this instance, a mother and her two children were wounded, an eyewitness says.
Many people in Somalia believe the air assault is merely aimed at showing Kenyans that the government is responding to the threat posed by al-Shabab.
They point out there was a similar strike after al-Shabab killed 36 quarry workers in Kenya's north-eastern Mandera region in December. Then, too, there were reports of civilian casualties, while Kenya failed to provide any proof of al-Shabab being hit.
This is in contrast to US air strikes in Somalia, which led to the killing of al-Shabab fighters and leaders.
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.
Garissa university campus
1. Militants enter the university grounds, two guards are shot dead
2. Shooting begins within the campus
3. Students attacked in their classrooms while preparing for exams
4. Gunmen believed isolated in the female dormitories
5. Some students make an escape through the fence