The death toll in the attack on a university in northeastern Kenya on Thursday rose to 147 and the siege has ended, said the country's disaster response agency.

"UPDATE: 147 fatalities confirmed in the Garissa Attack," The Kenya National Disaster Operation Centre said on its official Twitter feed. It added that the operation had ended.

Kenyan Interior Minister Joseph Nkaissery said ealier on Thursday that the number of dead in the attack on Garissa University College, in the northeastern town of Garissa, had risen to 79.

He also claimed that a final assault on a campus building where the Islamist militant gunmen had been holed out for over 12 hours was all but completed.

"The terrorists, 90 percent of the threat has been eliminated... we have been able to confirm that four terrorists have been killed," Nkaissery said, add adding that security forces that troops were continuing to search the campus as the total number of gunmen was not known.

"We are mopping up the area," he said, while at the same time warning that "the operation is ongoing, anything can happen."

"Dusk to dawn curfew"

At the same press conference, Kenya's police chief, Joseph Boinet, said the country had introduced a

dusk to dawn curfew for Garissa as well as the nearby counties of Wajir, Tana River and Mandera, each of which is located near the Somali border, as a security precaution.

The attack had begun in the pre-dawn hours of Thursday, when an unknown number of gunmen gained access to the university by using grenades to blast open the gates of the campus, before opening fire "indiscriminately," according to Chief Boinet.

Some students were able to escape, but at the press conference, Interior Minister Nkaissery said it was not yet clear how many were safe.

"Garissa University college has a student population of 815 and about 60 members of teaching staff, as of now we are able to account for 292 students and all the staff," he said.

'Hostages being held'

Earlier, both the Red Cross, which was leading the medical response to the incident and the Somalia-based Islamist militant group al-Shabab, which has claimed responsibility for the attack, said the gunmen were holding a number of hostages.

Al-Shabab spokesman Sheikh Abdiasis Abu Musab told the Reuters news agency that the Islamists were holding Christians only.

"We sorted people out and released the Muslims," he said.

10,000 new police officers

Kenyan President Uhuru Kenyatta responded to the attack by announcing that he had ordered the police chief to fast-track the recruitment of 10,000 new officers, noting that the country had "suffered unnecessarily due to shortage of security personnel."

Al-Shabab has pledged to punish Kenya for contributing troops to an African Union force fighting the militants in Somalia. The Islamist group also claimed responsibility for a deadly attack on the Westgate shopping mall in Nairobi in 2013.

pfd/ (Reuters, AFP, AP, dpa)