ABUJIA - Nigeria's militant sect Boko Haram has killed at least 85 people in five days in an apparent escalation of attacks in the Muslim-dominated north of the West African country.

The latest and deadliest came on Sunday morning when suspected gunmen of the sect stormed into the College of Agriculture in Yobe State, spraying bullets on students, some still sleeping.

Rescuers have collected 47 bodies of the students, mostly aged 18 to 22.

There were many others wounded in the attack who have been sent to hospital for treatment.

More corpses may be recovered as rescuers were still combing the area on Sunday afternoon for other dead or injured victims, a college official said.

On the same day, police confirmed 11 deaths after gunmen raided a village in Kaduna State the previous day.

Houses were reportedly torched in the attack on the village of Zangang, which had witnessed three other assaults by Boko Haram suspects this year.

On Wednesday and Thursday, at least 27 people were killed by Boko Haram insurgents in attacks on villagers in Borno State.

The killings echoed a threat by a man claiming to be the leader of Boko Haram, Abubakar Shekau, to launch more attacks in northern Nigeria until the sect installs and decrees strict sharia law in Africa's most populous nation.

Shekau, reported to have been killed by the Nigerian military, said in a video released on Wednesday, "I swear by Allah that there will be no democracy in Nigeria. We are going to rise against it ... It shall soon, very soon, be replaced by Government of Allah."

Boko Haram has caused thousands of casualties in northern states since launching insurgency in 2009. In the escalation of conflicts between its fighters and the military, Nigerian President Goodluck Jonathan in May declared a state of emergency in the northern states of Adamawa, Borno and Yobe.