Gunmen killed at least 40 people today in an attack on a college in northeast Nigeria, witnesses say, in a region where Islamist militants have targeted schools and universities.

Islamist sect Boko Haram has intensified attacks on civilian targets in recent weeks in reaction to a military offensive against its insurgency.

Boko Haram and spin-off Islamist groups like the al Qaeda-linked Ansaru have become the biggest security threat to the nation which is also Africa’s second largest economy and top oil exporter.

Gunmen stormed the College of Agriculture in Yobe state and shot students as they slept in the early hours of this morning, state police commissioner Sanusi Rufai said.

They also set fire to classrooms, a military spokesman in Yobe state, Lazarus Eli, told Agence France-Presse.

One witness counted 40 bodies at the main hospital in Yobe state capital Damaturu, and politicians claim that victims, most of whom were young men, were taken in van loads.

Boko Haram is fighting to overthrow Nigeria’s government to create an Islamic state, and has launched a number of attacks on schools including a raid which killed 27 students and a teacher at a school in Potiskum, a town about 30 miles from the site of today’s attack.

The group’s name translates as ‘Western education is forbidden’ and regard schools as a symbol of Western culture.

Across Nigeria thousands have been killed since Boko Haram launched its uprising against the state in 2009, turning itself from a clerical movement opposed to Western culture into an armed militia with growing links to al Qaeda’s West African wing.