More than 70 people have been killed in an attack by Somali-based Islamic extremists on a university in north-east Kenya, the country's interior minister has confirmed.

Joseph Nkaissery said that 79 people were wounded in today's attack and four suspected attackers have been killed.

He told reporters the total number of the attackers is still unknown and that security agents are fighting them at Garissa University College.

The minister ordered a dusk to dawn curfew in Garissa and in the nearby counties of Wajir, Tana River and Mandera.

Al-Shabab claimed responsibility for the attack.

The death toll now surpasses the 67 who were killed in al-Shabab's attack on the Westgate Mall in Nairobi in September 2013.