Gunmen have taken students hostage and killed at least 14 people at a university in north-eastern Kenya, aid workers and police say.
About 30 others were wounded after attackers stormed a university in Garissa town. Troops have surrounded the campus and are engaging the gunmen.
Witnesses spoke of the masked attackers firing indiscriminately and there are fears the casualty toll could rise.
Muslim and non-Muslim hostages had been separated, and 15 of the Muslim had been freed, said a spokesman for the group, which is part of al-Qaeda.
Exchange of fire
The militants, who have their headquarters in neighboring Somalia, have regularly targeted Kenya.
About five masked gunmen are said to have stormed the university.
A policeman at the scene told Reuters news agency that some students had been taken hostage.
“We can’t tell how many but they are many since the college was in session,” the unnamed policeman is quoted as saying.
The Kenyan Red Cross said about 50 students had been “safely freed”, but an unknown number were still being held, AFP news agency reports.
Kenyan police officers take cover outside the Garissa University College during an attack by gunmen in Garissa, Kenya, 2 April 2015.
Kenyans have repeatedly been targeted by al-Shabab.
Security forces were now trying to flush out the gunmen, a police statement posted on Twitter said.
It urged people to stay away from the area. The statement did not confirm that hostages had been taken.
Two guards were confirmed killed at the main university gate, with two policemen and a student among the injured. But eyewitnesses spoke of many casualties inside the building.
Some students without their shirts get out of a house where they seek refuge after escaping from an attack by gunmen in Garissa, Kenya, 2 April 2015.
Fleeing students took shelter in nearby homes.
I can hear gunfire from inside the campus. Ambulances are rushing in and out with the wounded.
One teacher told me some students managed to run away from the gunfire, and came to her house early in the morning to seek shelter.
But a huge crowd has gathered outside the house, mostly of people who are worried that friends and relatives may be still trapped inside.
Some of them are trying to enter the campus but the security forces are holding them back. Troops have also surrounded the main hospital, restricting public access to it as medical staff battle to cope with the wounded.
Most shops in Garissa are shut, and people are staying at home.
The town’s hospital has been sealed off.
The gunmen reportedly ordered students to lie down on the floor, but at least 27 are known to have escaped and are at a military facility.
“It was horrible, there was shooting everywhere,” student Augustine Alanga told the BBC’s Newsday program.
He said it was “pathetic” that the university was only guarded by two police officers in such a volatile area.
Kenyan Red Cross spokeswoman Arnolda Shiundu said there were about 30 casualties, four of whom were critical. Most had gunshot wounds, she told BBC World News.
Three people – two soldiers and a civilian – had been airlifted to the capital, Nairobi, she said.
The university opened in 2011 and is the only place of higher education in the region. It has some 700 students from across the country.
The BBC’s Anne Soy in Nairobi says that because of its proximity to Somalia, Garissa is an easy target for al-Shabab militants and there have been several attacks in the past.
She says that the UK and Australia issued alerts this week warning of potential terror attacks in parts of the country, including Garissa.
There has also been a specific alert for universities in the country.
Garissa, 150km (90 miles) from the border with Somalia, has a large population of Kenyan Somalis.
Al-Shabab has carried out a number of attacks in Kenya since 2011, when Kenyan troops were sent to Somalia to help fight the militant group there.
The deadliest attack targeted the Westgate shopping centre in Nairobi in September 2013, when 67 people were killed.
Al-Shabab is fighting to create an Islamic state in Somalia and is banned as a terrorist group by both the US and the UK.