The remaining 14 students who were kidnapped from a university in northwestern Nigeria were freed on Saturday, 40 days after being taken hostage, a local police spokesman told AFP.

Such seizures have become a frequent way for criminals to collect ransoms, with more than 700 abductions since December. Protesters have taken aim at security forces and blamed the government's inaction to crackdown on kidnapping gangs.

"Fourteen students of Greenfield University were released by their captors this evening," police spokesman Mohammed Jalige told AFP.

"They were dumped outside the city along the Kaduna-Abuja expressway" in central Nigeria, Jalige said he did not know if ransoms had been paid for their release.

On April 20, gunmen, known locally as "bandits" stormed the university and kidnapped around 20 students, killing a member of the school's staff in the process.

Five students were executed a few days later to force families and the government to pay a ransom.

It was the fifth such attack in around five months, and officials in Kaduna state called the executions "diabolical", though they strongly advised parents not to pay to avoid encouraging more seizures.

Armed gangs are terrorising inhabitants in central-western and north-western areas of Nigeria by looting villages, stealing cattle, and taking people hostage.

Since December 2020, 730 children and students have been kidnapped in Nigeria.

The President assures that @NigeriaGov will continue to work with State Governments to step up the protection of lives and property across the country, including educational institutions and other vulnerable targets.

— Presidency Nigeria (@NGRPresident) May 29, 2021