Gunmen from the militant Islamist group al-Shabab have killed at least 15 people and taken students hostage at a university in north-eastern Kenya.
Reports say 65 others were wounded when gunmen stormed the campus in Garissa. Troops are engaging the gunmen.
More than 500 students were still unaccounted for, a minister said. The number of hostages is unclear.
Al-Shabab, which is linked to al-Qaeda, said it was holding Christians hostage and freeing Muslims.
Hostages from the two groups had been separated, and 15 of the Muslims had already been released, a spokesman for al-Shabab told the BBC.
Live updates from Garissa siege
Exchange of fire
Garissa College University student Collins Wetangula said when the gunmen entered his hostel he could hear them opening doors and asking if the people who had hidden inside were Muslims or Christians, Associated Press news agency reports.
“If you were a Christian you were shot on the spot. With each blast of the gun I thought I was going to die,” he is quoted as saying.
Mr Wetangula said some security officers then entered through a window and took him and some other students to safety.
About five masked gunmen are said to have stormed the university.
Kenya’s Interior Minister Joseph Nkaissery told journalists that one of the militants had been killed as he tried to flee.
Out of 815 students, 535 had not yet been accounted for, he said.
It is not clear how many students were on the premises at the time of the attack.
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.
There are reports of continuing gunfights with some of the extremists firing from a university hostel roof.
Kenyan officials say security forces have isolated the gunmen in a single building at the university.
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. -BBC